How Do I Move My PLEX Server and Media To New Pegasus R4 NAS?

I'm a newbie to both Plex and iMac. Loving both so far...
I've started backing up my extensive DVD and BD collection to Plex on my iMac. I'm quickly running out of space on the Mac so purchased and set up a 12TB NAS.
How Do I Move My PLEX Server and Media To New Pegasus R4 NAS?
Any help would be greatly appreciated.
Thanks!