If you're a Firefox "sync" user, you could turn on "sync", sign in, and get your bookmarks that way by recovering them via the "Firefox Account" page under "Options".
If not, you might want to back off the version update. Click "Help" up top and then select "About". Note what version you've updated to, and visit the FF website and download and install an older version. Might be able to get some of the missing stuff back that way. Then turn on sync and let it sync (backup) your stuff.
Your bookmarks are probably still out there on your hard drive somewhere. FF is pretty bad at cleaning up old stuff, which might be good for you.