Wanhao Duplicator 6 / Monoprice Maker Ultimate thread pitch or number of steps?
If you navigate to e.g. the Marlin printer firmware configuration file for the Wanhao Duplicator 6 you will find that the steps per mm are defined as:

/**
 * Default Axis Steps Per Unit (steps/mm)
 * Override with M92
 *                                      X, Y, Z, E0 [, E1[, E2...]]
 */
#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80.0395, 80.0395, 400.48, 99.1 }


Sidenote, somebody who posted this has diligently tried to tune their machine, this should read:

#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80., 80., 400., 100. }


From these values you can tune your own if needed.

Now we do the math with the following assumptions:


400 steps per mm, 
standard 200 steps per revolution stepper motor (1.8&deg;) and 
assuming that your board uses 1/16 &micro;-steps


Dividing the physical stepper steps per revolution by the firmware steps per millimeter we can calculate how much the nut advanced in a single revolution, i.e. 200/(400/16) = 200/25 = 8 millimeter. The nut therefor advanced 8&nbsp;mm per complete revolution of the stepper. This means you will most probably have Tr8x8(P2) lead screws.

Do note that there are online calculators that can help you out doing the math for you, e.g. this RepRap calculator page.