Windows 10 backup/ reinstall disk

Hi,

I have a dell XPS 12 9Q33. It had windows 8 pre-installed. I have upgraded to windows 10. I have the reinstall disk for windows 8 in USB drive. I also have the windows 10 reinstall disk in USB drive. 

Now, if i want to use the BIOS option to reinstall windows Pressing f2/ f12 buttons) which windows will i get? Windows 8 or 10? After upgrading to windows 10, did my laptop also replaced pre installed windows 8 with windows 10?

Thanks

Sami