1. Go to File and choose Import and export...
2. Select Export to a file
3. Choose Favorites
4. Choose Favorites, not Favorites Bar to make sure all of them are backed up
5. Select a location for the file with all of your bookmarks. I'd recommend to click on Browse... and choose you mapped Z drive on the computer so the file is backed up and available from any computer you log in.
To recover your bookmarks, you just need to start on step 1 but then choose Import from a file... on Step 2.