A starting point:
http://docs.info.appl...fari/3.0/en/9263.html
However you'll need to know where the Firefox bookmarks file is. In older versions of Firefox there would be TWO files called 'bookmarks.html' on your computer. One would be tiny (because it was the bookmarks file which was initially present in an unused browser) while the other would be much bigger (because it was the one currently in use). However I've just run a search for 'bookmarks' on my PC (running Firefox 9.0) and it appears that the current file now has the date appended and uses the .json file suffix.
So you might need to locate that file, copy it to somewhere convenient (such as your desktop) and change the file extension to .html. Then you can follow the instructions in my link.
Chris