I just upgraded Firefox to the latest version and was instructed to create a new profile. After doing so, I noticed that all my bookmarks (for years) were wiped out. Impossible to get them all back.
One might say, “What about a backup?” Almost a fair question, but based on customary practice (compliments of Mozilla), I didn’t anticipate the need since I never had to in the past. Would there have been at least a simple notice to that effect, I would have.
This forum is not the right place to ask troubleshooting questions. If you have a problem with Firefox that you need help with, please ask your question on the Firefox support forum https://support.mozilla.org/questions/new .