How long after the Tower of Babel was Abraham's forefathers' time?
Abraham's forefathers, including Terah and Nahor, lived approximately 200 years after the Tower of Babel. At that time, Joshua 24:2 indicates they served other gods and were idolaters, with no known believers in the one true God remaining.
Les explains that the forefathers of Abraham—Terah, Nahor, and their family—dwelt on the other side of the river in old time, about 200 years after the Tower of Babel. Joshua 24:2 records God's declaration that they served other gods and were idolaters. Les notes that at this time, there was not a single believer in the one true God left, though someone questioned whether Seth might still be living.
And Joshua said unto all the people, Thus saith the LORD God of Israel, Your fathers dwelt on the other side of the flood in old time, even Terah, the father of Abraham, and the father of Nachor: and they served other gods.