I tried to restore my missing bookmarks from the most recent auto backup prior to the ugrade to Quantum. Told me "Unable to process". I need my bookmarks. Help.

I was just recently upgraded to Firefox Quantum and am now missing all of my bookmarks. I tried to restore my missing bookmarks from the most recent auto backup prior to the upgrade to Quantum. It told me "Unable to process". I need my bookmarks. Help. BTW I can't even create a new bookmark with this new updated version. I am not happy. Can you suggest how I can resolve this problem? If I cannot resolve it...how do I go back to the previous version?