How to map a network drive via nucleus

I’ve been told that I can access my external USB HDD by connecting it to the USB port of my cable modem/router. I’ve done so, and am trying to get Roon to see the drive. So far, I’ve tried (per the Roon examples), both \workgroup\GODZILLA and smb//workgroup/GODZILLA without success. In both, “workgroup” is the name of my local Ethernet network, and “GODZILLA” is the name of the drive.

What am I doing wrong?

Thanks - Boomzilla