Gotcha.
A ‘custom’ tv show is a challenge indeed.
Plex does not read the title of the episode from the file name.
However, since you have these files in .mp4 containers, you can embed the episode titles yourself and take advantage of Plex’s ability to read the embedded meta data from mp4 files.
You need a way to automatically read the episode titles from the file names and embed them as meta data into your mp4 files.
On Windows there is mp3tag which can do it.
It has a feature ‘Convert > Filename-Tag’
If you use the pattern %dummy% - %dummy% - %title% you will get exactly what you need.
The above will only work with mp4 / m4v files!