What did God say to Job about water molecules and where do I find it in
the Bible?

I am going to guess that the passage you are referring to is found
in Job 36:27. Here, Elihu says “He draws up the drops of water which
distill as rain to the streams; the clouds pour down their moisture and
abundant showers fall on mankind.” In this passage, Elihu appears to have
knowledge of the water cycle, which was not “discovered” by modern science
until the nineteenth century. This is one of many scientific supports to
the inspiration of the Bible. However, I do not believe one can
accurately claim that Job or any other writer of the Old Testament showed
knowledge of the existence of individual water molecules.

John Oakes