PMS PC to NAS connection

You should know what a SQL command is. Otherwise the learning curve is steep.

I recommend you to save a backup copy of the main Plex database file.
There is no need to backup the whole metadata folder.
And you absolutely have to stop/end/quit Plex server before making the backup copy!

https://support.plex.tv/articles/202485658-restore-a-database-backed-up-via-scheduled-tasks/