Sorry, Firefox updates your SYNC can't be restore. But Firefox stores your bookmarks locally, you can restore from that *https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks

If you have the bookmarks on another computer then you can create a JSON backup or an HTML backup and email that file to the other computer or copy the file to an USB stick and move the file that way. *http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox *https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile *http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox