quote; am not sure on the drain and how high the shower floor should be. An upstairs drain is right behind the wall and it is a 4 inch PVC drain. It goes straight into the basement floor.

Experts, permits, and inspections have other purposes other than raising taxes. They help you NOT make mistakes, such as HOW to not connect to that 4" PVC drain when you install the shower, and how to do it without raising the shower floor. Unless you have an unusual basement, raising the shower floor will result in a low shower ceiling.