Convert or Add Premium Library using Basic Library Files

I understand that a PMS Basic library cannot be converted to Premium. However, can I create a new Premium library and point it at the exact same set of folders used for my existing basic library? If so, what are the consequences? Details and conjecture:

I use iTunes on a Mac to rip CD’s from my collection. At this point, iTunes can be pointed at one of two media folder locations under /Volumes/Multimedia/Music/[libraryName]/iTunes Media. My existing Plex Media Server libraries point at …/Multimedia/Music/[libraryName]. One of these is a Basic library, since it was created before I purchased a Plex Pass. It contains about 3,000 tracks. The other is a Premium library with just a few tracks.

So, how do I best get the large library over to Premium? And, what do I lose in the process? For example, I have a LOT of CD’s in my collection that are by less known local artists. In most cases, iTunes cannot find an album cover, and often cannot even find CD Info and track names. I will add CD Info and track names when ripping in iTunes. Plex is much better at finding album covers or at least a photo of the artist, but I still have to search the web or take a photo, and change or add a new cover (Poster) in Plex. I am guessing I will lose much of this work if I switch my library to Premium.

Bottom line is that I would like to make the change now, before adding the rest of my collection of over 10,000 tracks. How best? Just create a new Premium library and point it at the same folders? Or, first delete my old basic library in Plex, and then create the new Premium library?

@KliffB said:
I understand that a PMS Basic library cannot be converted to Premium. However, can I create a new Premium library and point it at the exact same set of folders used for my existing basic library?

Yes, you can do that.
You can keep your old ‘basic’ library intact.

Each library in Plex can point to several folders. So you can easily combine the content of several media storage locations into one Plex library.

In general, I recommend you to write all metadata you find into your files directly. That way they are preservec, even if you have to rebuild a library or even change your media software altogether.

I further recommend you to additionally put album artwork as a separate .jpg file into your album folder. This jpg can be of a higher resolution than the stuff you embed into the files themselves.

So, basically: Organise your albums in folders and subfolders as indicated here
https://support.plex.tv/hc/en-us/articles/200265296-Adding-Music-Media-From-Folders
(Plex does not support the iTunes ‘Album’ property which combines tracks into an album. For Plex this is done both by putting all tracks of an album into a common folder and by tagging those tracks uniformly with AlbumArtist and AlbumTitle metatags.)

If they don’t have embedded metadata, put these in. They can be derived automatically from file and folder names with the right software.
It is also possible to generate proper file and folder names if the embedded metadata are already there and correct.

Here are some more tips regarding music

multi-disc albums
https://forums.plex.tv/discussion/comment/1050849/#Comment_1050849

handling singles and EP’s
https://forums.plex.tv/discussion/comment/1093611/#Comment_1093611

possible ‘side car’ files for music
https://forums.plex.tv/discussion/comment/1319703/#Comment_1319703

soundtracks and ‘various artists’
https://forums.plex.tv/discussion/comment/1472799/#Comment_1472799