Updating Firefox shouldn't erase any data on your computer. In most cases, if data is missing after an update, it's just because a new profile was created by mistake. It's easy to change the old profile back to the default for Firefox, without having to manually import data back in.

See the Recover user data missing after Firefox update for more information.

Thank you! It wasn't as easy as it seemed I tried it and nothing happened re-tried it and it worked... So scary!