I agree with @slipstick.
if you want to use stepper motors you will need a startup procedure in which each motor moves to the ZERO or HOME position so the Arduino can accurately count from 0. The zero position is usually identified by the movement triggering a microswitch of optical detector. Once the zero position is established the stepper will be able to move very precisely unless the load on it is so great that it misses steps.
...R
Stepper Motor Basics
Simple Stepper Code
also look up the AccelStepper library