I have done many windows 10 installs for 8.1 or win 7 users. My recommended procedure is simple:
Make a bootable win10 usb installer with latest version (1803). After booting, select "I don't have a key." Next, select the proper version, if need be. May depend on the win10 ISO you have. Assuming everything is backed up, delete everything on the drive. Tell it to install.
After install, update/install drivers. Next run windows updates. Finally, check to see if it is activated. If the machine had windows 8.1, and you installed windows 10 home in UEFI mode, it should grab the product key from the motherboard and activate. If windows 7, enter the key on the back to activate. (Home => home, pro and ultimate => pro.)
Also, if a windows 10 upgrade had previously been done, on any motherboard, whether from 8.1 or 7, that motherboard should then have a digital entitlement on MS servers. Connect to the update service after install and W10 will activate. Just be sure to install the right version (home vs pro).