If you formatted the PC it is unlikely that you will be able to retrieve the bookmarks, especially if you have used the drive again since formatting it.

A data recovery tool may be able to help, assuming that you have not added anything to the drive since reformatting it. If you try a data recovery tool, the file to look for is places.sqlite which will be in the profile folder

Thanks TonyE...I tried data recovery but I couldn't find any profile folder...I guess it had been replaced it when I formatted my PC. But I did somehow recover all my bookmarks! : ) I found this "bookmarks-2010-09-02.json" with the data recovery software. Apparently this .json file is all my bookmarks in firefox. Thank you for your help! ^^

It would be better to try to undelete a text file like a JSON backup in the bookmarkbackups folder instead of a large binary file like places.sqlite. Because all the MFT entries and index data is gone, your only option is probably a low level data search for specific content of such a .json backup.

You can open a JSON backup to see what the first bytes of such a file look like:

{"title":"","id":1,"dateAdded"

See http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox

See also http://www.recuva.com/