I'm sorry to hear that you have lost your bookmarks after installing a new version of Firefox. Here are some steps you can take to try and recover your bookmarks: Check for a backup: Firefox automatically creates backups of your bookmarks, which can be used to restore them. To check for a backup, go to the Bookmarks Library (press "Ctrl+Shift+B" on Windows or "Command+Shift+B" on Mac), click on "Import and Backup" and select "Restore". You should see a list of backup files. Choose the most recent one and click "Restore". This should restore your bookmarks. Check Firefox Sync: If you have Firefox Sync enabled, your bookmarks should be synced to your Firefox account. To check if your bookmarks are synced, go to the Firefox menu and select "Logins and Passwords". If you see your bookmarks there, you can restore them by signing into your Firefox account. Search your computer: Firefox stores your bookmarks in a file called "places.sqlite" on your computer. You can try searching for this file and replacing the current file with a backup copy (if you have one). If none of these steps work, unfortunately, it may not be possible to recover your bookmarks. In the future, I recommend creating regular backups of your bookmarks to prevent data loss.