missing "in"  -- (MW) The untranslated word "in" means "in," "within," "with" (an instrument), "by" (near), "by" (means of), "during" (time),  or "among"  with a dative object as the one here.  With the accusative, it means "into," "on," and "for." When referring to time, it means "during." It can mean "on," "at," or "by" in the sense of "near."

my -- "My" is the first-person possessive singular pronoun. This pronoun follows the noun so "of mine." As a genitive object of a preposition, as here, it means a movement away from something or a position away from something else.

missing "the/this"  -- (MW) The untranslated word is the Greek definite article,"the," which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more. 

Father-- "Father" is the Greek noun that means "father" or any male ancestor so "forefathers." It is the word that Christ uses to address his own Father.

's  -- The apostrophe "s" comes from the noun's genitive form. This case usually requires the addition of a preposition in English.  The most common is the "of" of possession for which an apostrophe "s" can be substituted.

missing "the/this"  -- (MW) The untranslated word is the Greek definite article,"the," which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more. 

house -- The Greek word translated as "house," refers to the building itself, all the people that dwell in it, including slaves and servants, all property owned by that family, and all the descendants of the continued line. We might say "estate" in English to capture this idea.

has -- (WW) The verb "was" here is the common form of "to be" in Greek. It means to have a certain characteristic or remain in a certain condition. It also equates terms or assigns characteristics.

many -- The word translated as "many" means many in number, great in power or worth, and large in size.

rooms:   --  (CW) The Greek word translated as "mansions" is only translated as mansions, rooms, or apartments here in John. The closest other Greek references to this idea of rooms is from the military use as billets or quarters, that is, a longer-term stopping place where soldiers stay separately. This is opposed to staying in a military camp, where everyone stays together. In the form used, this word could be an adjective, a verb, an adverb, or a noun.  Across most of its forms the primary sense of the root word is being alone, solitary. As a noun, it carries a sense of both tarrying, staying for a temporary time, and of persistence and permanence. Hence, it is both a stopping place and a longer-term staying place. From its other meaning, the noun means a place to be apart either temporarily or longer term.

if -- The "if" here expresses a condition but it means nothing regarding whether that condition is met or not. When citing a fact with a declarative verb instead of one of possibility, the sense is more "since" or "as sure as." When this word is paired with the conjunction translated as "but" below, the structure works like an "if then" statement in English.

missing "however"  -- (MW) The untranslated word "however" means "but," "however," and "on the other hand." It joins phrases in an adversarial way. Since it always falls in the second position, translating it as "however" often captures its feeling better.  It can also be an explanation of cause ("so").

that were -- (IP) There is nothing that can be translated as "that were" in the Greek source.

not --  The negative used here is the Greek negative of a subjective opinion, commands, and requests Used in negative "when" and "if" clauses.

so -- (IW) There is nothing in the Greek that can be translated as "so" in the Greek source.

would  -- "Would" is a particle used with verbs to indicate that the action is limited by circumstances or defined by conditions. There is no exact equivalent in English but "possibly" is close. This word works similarly to the "might" or "should" of a subjunctive verb, but we don't want to confuse it with the subjunctive so using "possibly" provides a consistent translation.  This particle usually suggests the subjunctive form of the verb but can be used without it. The same Greek letters can always be the more common conjunction meaning "when," so this meaning comes from context.

I -- This is from the first-person, singular form of the verb.

have -- (WT) This helping verb "have" indicates that the verb is the tense indicating an action completed in the past. This is not the tense of the verb here.

told - The word translated as "told" means "to say" and "to speak." It is one of the two most common words translated "speak," "say" and "tell," but it has more a sense of addressing and proclaiming.

you. - The Greek pronoun "you" here is plural and in the form of an indirect object, "to you," "for you," etc. As the object of a preposition, this form implies no movement, but in a fixed position or events occur at a specified time or while the action was being performed.

that --  The word  "that" introduces a statement of fact or cause, "for what," "because," "since," and "wherefore."

I -- This is from the first-person, singular form of the verb.

am  -- This helping verb indicates the present tense of the verb. It is used here to form the present, progressive tense, which doesn't exist in Greek but which can smooth the flow of English sentences.

going  -- The Greek verb translated as "go" is the most common verb translated as "go" in the NT. This word means "to lead over," "depart," and "to carry over." However, this word uniquely means "to pursue a course" and "to depart from life." In the active voice, it means "made to go" or "carried over" but in the passive or middle,its normal form, the subject is either being taken or taking himself and means "going," "crossing over," or "departing" more directly.

there -- (IW) There is nothing in the Greek that can be translated as "there" in the Greek source.

to -- This "to" is added because the verb's infinitive form requires a "to" in English.

prepare  -- The verb translated as "to prepare" means to "get ready," "prepare," "make ready," and "to cause to prepare." It is in a form that indicates the action has been completed.

a -- There is no indefinite article in Greek, but when a noun doesn't have a definite article, the indefinite article can be added in English translation.

place -- "Places" is translated from a Greek word that means "place," "position," and "topic." This is a fairly uncommon word for Christ to use.

for -- This word "to" comes from the dative case of the following word that requires the addition of a preposition in English. The most common is a "to" for the English indirect object. However, the translator can choose other prepositions: "with,"  "in,"   "of,"  "as," "by," "for," "at," or "on" depending on the context.The sense here is "for" a benefit.

you. -- The Greek pronoun "you" here is plural and in the form of an indirect object, "to you," "for you," etc. As the object of a preposition, this form implies no movement, but in a fixed position or events occur at a specified time or while the action was being performed.