What is the proper steps/mm to use when using the Golmart 1204 ball screw with 32t GT2 Pulleys?

I have to make a lot of assumptions to come up with a number

800

I have assumed the following

16x microstepping

200 steps per revolution motors

matching toothed pulleys since you only mention 1 size, one on the motor and one on the transmission shaft. meaning there is a 1:1 gear ratio

That is what I came up with with the RepRap steps calculator. They are 1204 Ball screws with 4mm pitch

It depends on your stepper setup. Is it 1/8, 1/16 or 1/32?