Don't know if it will work with a USB numpad, but there's a freeware program called Sharpkeys that I use on my laptop to make the Capslock key into a Windows key. It might do what you're looking for.

A USB-C cable is a recent type of USB connector that's easier to use and more powerful than older USB types. USB-C cables can be used to quickly charge many popular devices, including the MacBook Pro ...