You can't even buy Windows 8.1. Well there might be a few disks still on bottom shelves somewhere. I have the disk and I can use it again and again,,,,but,,, you have to authorize it once installed and that is ( Last time I checked) the same price as Windows 10.
Windows 10 is still free for those who use assistive technologies.. cough,,, cough,,
https://www.microsoft.com/en-ca/accessibility/windows10upgrade So it's a no brainier. They were super helpfull when I used Chat to authorize a Windows 7 desktop. They used the W7 serial number I read off the side of the case.
The download installer seems to hang at 99%. Hundereds of posts about it with no easy solution. so-
Best to download the ISO image of Windows 10 and burn it to a DVD. The ISO copy containes both the Home and Pro version. So depends on which version of W7 you have.