I can't add open scenes in "Build Settings"

I have 2 scenes with main menu and main game, I can’t add open scenes, I have tried to drag it, but it has no results. Please someone help me. I have attached screenshots here:

It looks like your two scenes are not in the same Unity project. You can only add scenes to the build menu that exist within a single project.

There is a way to export assets from one project to another, but I don’t have much experience with this so you’ll have to refer to the documentation: