This is another opportunity to examine both the Hebrew and Greek. There are two different Hebrew words here, baqash and darash both translated as "seek." There is a play on words here in the Greek contrasting the ideas of "out" and "in".
According to the Hebrew bible site, Mechon-Mamre, this literal version of this verse is:
"And ye shall seek Me, and find Me, when ye shall search for Me with all your heart."
וּבִקַּשְׁתֶּם אֹתִי, וּמְצָאתֶם: כִּי תִדְרְשֻׁנִי, בְּכָל-לְבַבְכֶם
Also (and) ἐκζητήσατέ (you will seek out) με (me) καὶ (and) εὑρήσετέ (you all are going to discover) με (me) ὅτι (seeing that) ζητήσετέ (you are going to seek) με (me) ἐν (in) ὅλῃ (whole) καρδίᾳ (heart) ὑμῶν (of yours)
And you are going to seek me out and you are going to seek discover me because you are going to seek me in that whole heart of yours.
There are two different Greek verbs translated as "seek." The second word is the simple version, without a prefix that means has a variety of meanings around the idea of "searching" and "desiring."It has a sense of seeking with a specific aim. The initial word has dds the prefix that means "from" or "out of" so its meaning means is "seek out."
The term used for "find" is the source of our word, "heuristic," meaning enabling a person to find out something for themselves. It means "find out" and "discover."
However, from the point of view of Christ's teaching, the most interesting word here is "heart," specifically "whole heart," which is a phrase used in Mark 12:30 And you shall love the Lord your God with all your heart. There is an article about that word and related ones here.