You will need the programs folders if you migrate the windows OS.
And possibly some more data depending on your specific present windows setup.
Why do you want to do it this way only migrating the clean OS ?
IMHO its much easier to download Windows10 install on a USB stick and initiate a fresh windows from that.
That will kick out any mess from other programs and any nasty trojans you may not know of.
(Windows defender only protects you against vira, not trojans)
This download is free, as it does not have a key and dont require one for install.
If you dont know your windows key, it will most likely be a digital key bonded to the CPU internal serial number.
That means the fresh windows install will recognize the install key from your cpu.