Take with you seven pairs of all clean animals, the…

So, recently I have decided to read through Genesis again, been at least a year or two since I’ve been through it. (Not saying I don’t read or study, just haven’t been in Genesis in a long time). I hit Genesis 7 tonight and something stuck out to me that bothered me. How could Noah have an idea about what animals were clean and unclean? Since the law was not given until Moses. “Take with you seven pairs of all clean animals, the male and his mate, and a pair of the animals that are not clean, the male and his mate,
Genesis 7:2

Take with you seven pairs of all clean animals, the male and his mate, and a pair of the animals that are not clean, the male and his mate,