"We now know that dinosaurs became extinct millions of years before human beings appeared on this planet."

No we don't know that.  That would mean death before sin, and the Bible is clear that death came because of one man's sin:  Adam.  And even evolutionists don't claim that Homo Sapiens existed "millions of years ago."  It would also mean that Genesis is wrong, no matter how it is interpeted, since it has birds before land animals.  Evolution claims that birds evolved from dinosaurs, in spite of the lack of evidence and the insurmountable changes that would have been needed to change from reptile to bird.  .And the methods for dating fossils are unreliable. This has been proven over and over.

Whether or not the ancient Hebrews believed that the earth was flat or not, is irrelevant, since the Bible does not teach that.  They believed a lot of unbiblical things.  Jesus called them on it more than once.