generate lightmap uvs?

when i import my scene from max, it allows me to select the generate lightmap option, but when i select any child of it, the option isnt there?

do i have to individually import every mesh in the scene?

In your project window ,you select your fbx model.Then you can see “FBXImporter” in the Inspector window.You find the “generate lightmap UVs” in it and check it.