maybe you can take a look at the link below there is pretty much everything about a 3.5 inch touchscreen and volumio.
or watch the tutorial, and to my knowledge you can skip (sudo apt install lightdm) as a penultimate line.
https://drive.google.com/file/d/1-m1Mom41RZn2TwUtbIGZe0G4fIGFuL4Q/view