xps 12. How do I factory reset (Windows 8) after upgrading windows 10?

I want to reset my xps 12 laptop to factory, which shipped with windows 8.  I first tried the Dell Backup and Recovery. I saw the only recovery choice was the factory image, which is what I want.  It rebooted, however then it seems Windows 10 stuff takes over and I can't factory reset.  I can't roll back to 8 since I'm past 30 days in Windows 10.  Not sure what to try next.