Backup Roon Rock Intel NUC to External USB - Win11 and MacOS

I am sure this has been posted many times, but it is a rabbit hole…

I am looking for a command line to backup my entire library of 3.5TB+ to an external USB drive for either Windows 10-11 and MacOS.

It appears that I cannot simply connect the external drive to my Roon Rock USB port. In my mind this would be the most efficient way to backup, rather than spend a day using up network activity…

Can anyone provide a command line for both windows and macos with some kind of automation?

Thanks a lot, sorry if this has been asked a kazillion times already. :thinking: