Try https://support.mozilla.org/en-US/kb/recover-lost-or-missing-bookmarks followed by https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data and https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

Good luck with that, If need help working with those files report back and someone else with more experience will help, may have to wait.

Please let us know if this solved your issue or if need further assistance.

I have read each of the above problem-solving pages several times, and have tried several proposed solutiongs, but am still unable to find a working solution. Admittedly I am not tech-savvy -- perhaps I am simply unable to follow instructions properly.

You can check for problems with the places.sqlite database (bookmarks and history) in the Firefox profile folder.

• use "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page
• https://addons.mozilla.org/firefox/addon/places-maintenance/

See also:

• http://kb.mozillazine.org/Locked_or_damaged_places.sqlite
• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file

If "Verify Integrity" on the "Help -> Troubleshooting Information" (about:support) page or Places Maintenance can't repair the places.sqlite database then remove all places.sqlite file(s) in the Firefox profile folder to make Firefox rebuild the places.sqlite database from the most recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created
• http://kb.mozillazine.org/Unable_to_process_the_backup_file_-_Firefox

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder
• http://kb.mozillazine.org/Profile_folder_-_Firefox