iMovie does not give the option to change quality

Version: iMovie 10.1.8

I am trying to follow the advice of other posters here to export my movie as an mp4 format, and I keep finding advice to export to quicktime, which 10.1.8 does not have, or to export and change the quality.

For some of my projects - specifically the one that I'm trying to export rightnow - I don't see the option to change quality when I go to share it, and I haven't been able to find a reason why. This is not the same for other projects, even ones that I have essentially duplicated this project from.

Does anyone know why and how I can fix it (or better yet, how I can change my .mov to .mp4)? I've tried exporting at 720p vs 1080p and it still exports as .mov 😐