Maybe use a removable USB drive to transfer the bookmarks if you aren't able to do this via Sync. Note that Sync isn't meant to be used as a backup device, but merely to Sync personal data between connected devices. For the bookmarks you can use a recent compressed .jsonlz4 backup in the backups in the bookmarkbackups folder or create a backup yourself. *Bookmarks -> Show All Bookmarks -> Import & Backup -> Restore On Mac, Import & Backup is the third (star shaped) button on the toolbar in the Library. If you want to use a USB drive then see: *https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the <b>about:preferences</b> page. *Help -> Troubleshooting Information -> Profile Directory:<br>Windows: Show Folder; Linux: Open Directory; Mac: Show in Finder *http://kb.mozillazine.org/Profile_folder_-_Firefox