You cannot mix movies and TV shows in the same library. It is not supported and will cause problems with recognition, sorting, metadata download, etc.
To give you a specific example:
F:\TV SHOWS PLEX\ <-- Folder added to TV show library
...The Handmaid's Tale {tvdb-321239} <-- ID optional, helps with matching
......Season 04 <-- "Season" in English; two digits for season number
.........The Handmaid's Tale s04e01 Pigs.ext <-- sXXeYY mandatory; ext=mkv/mp4/etc
Use the show name as it appears in thetvdb.com or themoviedb.org. If the show name has an illegal character such as a colon, just leave it out. Do not substitute a space, dash, etc.
Also, if the show already exists in the Plex library, perform the Plex Dance after renaming and reorganizing.