How to retrieve the serial number of my NAS?

I need to retrieve the serial number of a NAS.

From another PC, I wrote:

wmic /node:x.y.z.k bios get serialnumber

but I get this message:

ERROR:
Code = 0x800706ba
Description = The RPC server is unavailable.
Facility = Win32

I went to the server farm because I needed it quickly, but I'd like to know if I could solve it from a remote PC too.