Go to Start and open run. Type in %appdata% and enter, here go to the folder Mozilla/Firefox/Profiles, open the profile folder and you will find a folder called bookmarkbackups. In here are all the bookmark backup files Firefox created for you.

Give this a read as to how to use them.

Restore bookmarks from backup or move them to another computer

Export & Save your Bookmarks in an HTML file on your Old Computer

Exporting Bookmarks to an HTML file

• https://support.mozilla.com/en-US/kb/Exporting%20bookmarks%20to%20an%20HTML%20file

Copy/Paste the Saved HTML Bookmarks file on your New Computer. Now when you are on your New Computer, Open Firefox & Import Bookmarks from the Saved HTML Bookmarks file

Importing Bookmarks from an HTML File

• https://support.mozilla.com/en-US/kb/Importing%20Bookmarks%20from%20an%20HTML%20File

Check and tell if its working.