Hi, System Restore can sometimes cause problems, especially if you restore to before a Firefox update. You can try this first: Open bookmarks > Show All Bookmarks > Import and Backup > Restore, and see if you have a backup there.

If not, just right click > Copy, the places.sqlite file.

• Profiles - Where Firefox stores your bookmarks, passwords and other user data.

• Recover important data from an old profile.

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I can copy, but where do I paste? Also, when I try to open the file, Windows can't open it. Which program do I use to open it?

This is possibly caused by restoring an older copy of the profiles.ini file.

• https://support.mozilla.org/kb/how-run-firefox-when-profile-missing-inaccessible

You can copy the file to the current profile folder, but you can also re-register that previously used profile to make Firefox use that profile. You can do that by using the Profile Manager to create a new profile and click the "Choose Folder" button and browse to that previous profile.

• http://kb.mozillazine.org/Profile_Manager

You can use this button to go to the current Firefox profile folder:

• Help -> Troubleshooting Information -> Profile Directory:
  Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder

You can copy files like these to the current Firefox profile folder to recover specific data.

• bookmarks and history: places.sqlite
• bookmark backups: JSON backups in the bookmarkbackups folder
• SQLite files like cookies.sqlite (cookies) and formhistory.sqlite (saved form data)
• logins.json and key3.db (decryption key) for Passwords saved in the Password Manager
• cert8.db and possibly cert_override.txt for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words you added to the spelling checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other Site Preferences
• sessionstore.js for open tabs and pinned tabs and tab groups

See also:

• https://support.mozilla.org/kb/Recovering+important+data+from+an+old+profile
• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox