Cant combine these objects to 1 layer

[Feldspar69]

Hi, I received this output from a map generator and it appears that all the different buildings have been placed into their own layer and I cannot find a way to combine them into 1 layer. as u can see Merge selected is greyed out for some reason. Does anyone know a fix to this?

[Kurt Gold]

The Merge Selected command refers to genuine layers (technically speaking) and not objects.

All your buildings are objects and not layers.

You may group them.