The steps per unit for X and Y will be 20,000

The way that is worked out is 2000 steps to move the motor 1 rev, you have 2:1 gearing so that means 2 motor revs to one screw rev so to turn the screw once it will need 2000 x 2 = 4000

Your pitch of screw is 0.2inch so it will take 5 turns to move 1 inch so steps per inch are 4,000 x 5 = 20,000 steps per inch.

Hood