Somewhere along the line, Firefox changed its method of storing its Bookmarks (Favorites, to the IE users).
Originally, Firefox simply saved them as a file bookmarks.html in the individual users profile directory c:\users\[userID]\AppData\Firefox\Profiles\[profileID] in Windows 7 (and in the corresponding structure in earlier versions).
Then, Mozilla changed to storing the data in a micro database instead of in an html file. That makes backup and restore a little more complicated. But, it’s still not bad.
Firefox offers two ways to back up the bookmarks. First, it has a Backup function that is accessed via the Menu Bar. Select Bookmarks and then Show All Bookmarks. Then, on the resulting Library page’s menu bar, select Import and Backup.
That will open an options menu — the first option is Backup…, which will open a file save dialog box to save your database backup. This backup will be in .json format, which is not directly usable.
The .json file can be restored to your computer, or to another computer, later. The second entry on that options menu was Restore.
The other backup option is to save the file as Bookmark.html. You find this option along a similar path. On the Firefox Menu Bar. select Bookmarks and then Show All Bookmarks. Then, on the resulting Library page’s menu bar, select Import and Backup. Now the route changes, instead of clicking Backup, click Export Bookmarks to HTML…