I have a full DSM 6 → DSM 7 How-To here in the forum which tells you what the installer will do and what you must do after it completes (you grant “PlexMediaServer” permission to your media.
Documentation on what changed:
Documentation on the actual process.
At this point, I will ask:
Do you still have the Plex shared folder intact ? (fully populated with all your old DSM 6 server metadata and databases)
Does user Plex exist ?
Unless you’ve deleted files, recovering / repairing won’t be a problem.
Depending on the amount of data , it might take some time for the NAS to complete all the file moving.
