Where? That faith of yours?
In the parallels (Matthew 8:26, Mark 4:40), this verse contrasts two of the Jesus terms of opposition: faith versus fear. here, the "fear" is left out except in the narrative. This verse is a good example of how Jesus's words in Greek are what was spoken, but the translation that we read in English is made to sound good in writing.
The word translated as "where" means "where", "at what point," and [of manner] "how."
Untranslated is the Greek article, "the," which usually proceeds 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"). Here the form is plural so "those". See this article for more.
The term translated as "faith" is closer to our idea of having confidence or trust in people, especially their word, rather than having a religious belief.
The word translated as "your" is plural addressing all of Christ's listeners. This pronoun can go in front or after the noun, depending on the emphasis.
ἡ (article sg fem nom) "Unto them that" is the Greek article, "the," which usually proceeds a noun and, without a noun, takes the meaning of "the one" or, in the plural, "the ones." Here it is separated from its noun by a conjunction. -