Help upgrading from windows 7 to 10 with parallels 12.2

I am trying to upgrade my Parallels 12.2 with WIndows 7 VM installed to Windows 10. I purchased and downloaded Windows 10 (ISO file).
Following the steps in Parallels, I managed to simply add a new VM for Windows 10. This is not what I wanted to do, I wanted to upgrade my Windows 7 to WIndows 10, keeping the same files and other programs in the Windows 7 VM.
I don't see an option in Parallels 12.2 to upgrade an existing VM.
If this is not possible is there someway to copy the files over from Windows 7 VM to Windows 10 VM?
Do I have to buy a newer version of Parallels? How much more do I have to spend?
THanks, Grayson