You can start from the chapter that picks up right where the movie ends. Usually, you can find this information in fan discussions or on manga-related forums.
One key event is Yuji swallowing Sukuna's finger. Another is the various battles against powerful curses like Mahito. Also, the Shibuya Incident is a major event where many characters face great challenges.
Well, in Jujutsu Kaisen full story, Yuji's life changes completely when he swallows Sukuna's finger. At the school, he has to train hard to master jujutsu techniques. The story also involves the exploration of the origin of curses. There are different grades of curses that the students have to face. And there are different factions within the jujutsu society with their own agendas. For example, some want to use Yuji for their own purposes while others are more interested in eradicating curses in a more traditional way.
The Jujutsu Kaisen manga is indeed ending. It's been a great run, but all good things must come to an end. The final chapters are bringing closure to the characters and story arcs.