MozBackup - A backup/restore tool for Mozilla FirefoxMozBackup is a software for creating backups of Mozilla Firefox, Thunderbird, SeaMonkey,Mozilla suite and Netscape profiles. It makes backup of bookmarks,mails,contacts,history,extensions,cache etc and it's easy to restore this backup too. There may be other ways of backing up bookmarks too but i found it way easy for doing so.
You can backup this file using the same procedures mentioned above instead we've to choose the restore option in step 2.
Download MozBackup here