What's the noun for trilogy? Here's the word you're looking for.
trilogy
A set of three works of art that are connected, and that can be seen either as a single work or as three individual works. They are commonly found in literature, film, or video games.
“I find that I like duologies a lot better than trilogies and quadrilogies so I was wondering if anyone could give me a list of some.”
“He started out making no-budget splatter films, only to go on to helm one of the most successful cinematic trilogies of all time.”
“The portentous original plan was to make three trilogies and so far we've been subjected to all three of the middle trilogy and, more recently, two of the first.”