You seem to be getting things in a bit of a twist. The "steps" are nothing to do with Mach 3, they all depend on your motor and driver, If you have the motor and the driver, then you can find this out yourself by connecting up the motor and driver, then putting a number of pulses into the "step" input of the driver card, and seeing how far the motor moves. The advantage with a stepper motor is that it will move for one step. So you can mark the output shaft, then put pulses into the motor. The shaft will move round step by step until it comes back to where you started. You could even use a push button to put the pulses in.
What Mach 3 does need to know is how many "pulses" therefore the number of "steps" Mach 3 has to put out to drive your axis either 1mm or 1 inch, depending on which measurement your wish to set up in.
I have not heard of a 5 phase stepper, most are four, or two - but for example - my drivers are set to 1/8 step, my motors need 200 steps per rev, I have a geared down drive to my axis of 3 to 1, and the axis has to turn 10 time to move one inch. Therefore I need 8 x 200 x 3 x 10 = 48,000 pulses to move one inch. As you can see then, my best resolution is about 1/5th of a thousanth of an inch.
If this a a bit difficult to work out, there is a setting system built into Mach 3 to set the correct number of "pulses per unit" when you are setting up each drive (all drives need not be all set up in the same way).