Connecting NAS WD PR4100 to another to expand storage

OK, here is my situation. I have a 32TB WD PR4100 that I use exclusivly for my Plex media Server and I am down to 1TB remaining space. I would like to add another 32TB of storage for future growth. I am now over my head??
Can I connect another NAS via USB wothout creating a seperate drive?
If I can connect anopther NAS that will only act as storage, not a server… what is the least expensive reliable option for that?
And if all the above are true or kinda true… can someone tell me where to look for laymen configuration of my new extended server?

Thanks in advance to all the experts here who I know will get me set up with the best possible solution.

Regards,
wniels

AFAIK you can’t connect another NAS via USB, but you can use NFS to mount 1 NAS to the other.