You are using mp4 files. The titles that you see are most likely embedded meta tags in your files.
First thing should be to edit the tv show library in Plex and disable “Prefer local metatags” (on the “Advanced” tab) That way embedded meta tags will no longer override data from Plex.
Look up your show both on TMDB The Magilla Gorilla Show (TV Series 1964-1966) — The Movie Database (TMDB)
and on TVDB Search - TheTVDB.com
(annoyingly, there are two versions on TVDB)
Plex uses by default TMDB for tv shows. Check if your episodes fit either the TMDB or TVDB listing better. Then change the season and episode numbers of your files accordingly.
(Judging by your screenshots above, you will like TVDB better.)
Plex Dance the whole show.
Navigate to the top level of the show in Plex and “edit” it.
Go to the Advanced tab and switch “Episode Ordering” to “TheTVDB (Aired)”
Refresh Metadata of the whole show.
