I’m trying to finish grabbing a show, but Sonarr says the final season is #3, while the rest of the internet (i.e. torrent sites) says that season is #5. It looks like the first 2 seasons were split up into 1/2 seasons when originally shown. So while Sonarr is looking for Season 3, it’s finding the first half of what it thinks is Season 2.
You can manually import them to the correct episodes. You should be able to go off of episode names. Sonarr uses the TVDB and that is also what Plex/Emby/Jellyfin use normally so those are the numbers you probably want.