How can I determine which wires on my stepper motor bellong to A+ A- B+ or B-?

You can use a multimeter to determine the wires of the same coil (i.e A+ and A- belong to he same coil). The wires that are connected on the same coil will have relatively low resistance. A wire from one coil to another coil with have no continuity since the two coils are not touching each other.