Thank you for the question on the statement, “If it is not in the Bible, don’t believe it”?
That statement is false. There are many facts that the Bible is silent on which is true. King Solomon’s observations on plants and animals recorded in Proverbs reflects that there are other observations that’s not recorded.
Psalm 19 states that the heavens continue to reveal knowledge even though it does not have a voice. Scientists are uncovering those knowledge.
For a person to accept that statement would be denying people, places, and progress or inventions that has been invented by individuals.
The biblical statements focuses on a particular people group and the surrounding people or nations that impacted it. Those statements are true and some of those statements are contested by science. As science continue to uncover them, they may or may not affirm the biblical statements.