As these files are owned by user plex, and others can only read them, you’ll have to use sudo to perform any actions which will modify the files. Likewise, if the directory to which you are copying the files doesn’t allow you to write to it, you’ll also need to use sudo.
As an example, if you wanted to copy all of these files to a directory owned by plex on your new server, you’d do something like (from the directory where the database files are stored; ensure Plex Media Server is stopped when you do this):
sudo cp * /path/to/new/server/data/directory/
But do you really only want to copy the database files to the new installation? Or are you attempting to recreate your existing server on the new system? If the latter, have a look at this forum post for a procedure to move your entire Plex data directory:
Or see this support article for the more generalized version:
https://support.plex.tv/articles/201370363-move-an-install-to-another-system/
