To add on to this answer (which is correct):
Your “of” can also just be a regular file if that’s easier to work with vs needing to create a new partition for the copy.
I’ll also say you might want to use the block size parameter “bs=” on “dd” to speed things up, especially if you are using fast storage. Using “dd” with “bs=1G” will speed things up tremendously if you have at least >1GB of RAM.
Simple thing, but are you sure you mounted the NFS share as NFSv4? I don’t have access to a machine to check right now, but I think it might default to mounting NFSv3, even if both sides support v4.