Click start/search/all files and folders and type bookmarks into the search box and press the enter key. Look for the latest bookmarks.htlm file that has a Firefox logo on it. Right click on the file and choose copy. Paste the file to mydocuments or wherever you like.
Open Firefox and click bookmarks/organize bookmarks. Click file/import/from file and browse to where you pasted the bookmarks.htlm file. Click on it and click open. That should do it.