It will depend on what your stepper is driving. For example, if you have a 5mm pitch dia. pulley on the stepper, driving a sycronous belt, the required rotation of the stepper would be:
360*(1/(5Pi)) = approx. 22.91831°
I don't use steppers, but I'm assuming that each 'step' is 7°. If this is the case - you'd need approx. 22.91831°/7° = approx. 3.27404 steps.
Any crank, cam, or ellipse will not yeild a consistent
linear movement per. degree of rotation. A screw for
this application would need a pitch of 51.42857142875...
mm., an infinitive number.