Firefox bookmarks are not automatically backed up with User Data. Follow this guide to manually back them up.
- Press the "ALT" key to bring up the Firefox Menu at the top of the browser.
- Choose the "BOOKMARKS" item.
- Choose "SHOW ALL BOOKMARKS".
- A new window will pop up. At the top of the new window, click the "IMPORT AND BACKUP" button.
- In the menu, choose "BACKUP".
- A new window will pop up. Navigate to your DESKTOP folder and save the file. Keep the default name (example: "bookmarks-2015-03-05").