Have you tried using the Firefox Bookmark Manager? ctl+shft+o then the menu at the top > Import and backup > restore : choose file.

https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them

See also

https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data#w_what-information-is-stored-in-my-profile (also the sections how do I find my profile | ... without opening Firefox) https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

Did you also look on the hard drive in case there are profiles that aren't registered?

• https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update
• ~/Library/Application Support/Firefox/Profiles/<profile>

You can check if you have an "Old Firefox Data" folder on the desktop in case the Refresh feature in Firefox has been used and a new profile has been created.

• https://support.mozilla.org/en-US/kb/reset-firefox-easily-fix-most-problems

If you use the Time Machine or other backup then try to restore file(s) from this backup.

• https://support.apple.com/guide/mac-help/restore-files-mh11422/mac