Take a look at this
windows 10 stuck at login screen does not recognize mouse or keyboard - Windows 10 Forums
Do yo have another keyboard or borrow a friends? They are suggesting
to use a PS/2 keyboard/mouse or a USB-to-PS/2 adapter to pass the installation phase. Afterwards, your hardware will work again. That's a round connector.
You could buy one and return it if it doesn't work. If you can get it to work are you going back to windows 7?