A recent Firefox automatic upgrade seemed to have deleted all my 100+ bookmarks and none of the solutions on here seemed to work (this search wasn’t exhaustive by any means, so forgive me if this has already been posted). I went to Bookmarks>Show All Bookmarks>Import and Backup>Restore>Choose File and was told no file available. Previously, I’d already clicked through Help>Troubleshooting Information>Open Folder (adjacent to Profile Folder)>Bookmarkbackups and noted the pathway: C:\Users\(my name)\Appdata\Roaming\Mozilla\Firefox\Profiles\(long file name), so I knew where a backup existed. I then went to File Manager (is it still called that?) and clicked to C:\Users\(my name). As Appdata must be a hidden subdirectory, I had to type it in the bar at the top after my user directory name. That led in the end to find that there were two subdirectories in ‘Profiles’ – one of which was empty and the other with a list of dated backups. I reasoned that the Bookmarks Restore mechanism was looking in the empty sub, so I copied the latest backup file into this empty sub. I then went back to Firefox Bookmarks and did the ‘Show All Bookmarks>Import and Backup>Restore>Choose File’ thing and the copied file was displayed. I clicked on it and Hey Presto – Bookmarks restored! This is probably a long-winded way of doing it, but hey, it worked.