I cannot help much with MS-Win, but I do know that you CAN install/boot MS-Windows (most versions) on an external USB drive, using (free) WinToUSB software to do the install.

So, one way to accomplish that here, would be to first partition the new 3TB drive with enough space for your new "C:" system drive, and then use WinToUSB to install MS-Windows onto it. Then copy/reinstall anything else you want, and create any extra partitions for data etc..

Hopelessly complicated perhaps, but it does work.
Others here, who actually use MS-Windows, will probably have better suggestions!