[mactec54]

My whole wires are unshielded I check. It will be helpful if you tell me how to ground sheilded wire of stepper motor.

Do I have to connect one end to motor and the other end to connected to ground? Or one end connect to shield wire and the other end connect to ground?

First you have to have a Ground Plane, where everything is mounted too in your Box is the Ground plane, check the incoming main power supply Ground is mounted metal to metal this then Ground the Box this is important to have a Good Ground anything then that is in the box can be Grounded to a Ground Bus or stud this has to be done correctly or it will be ineffective I will post some snips of how the shields have to be Grounded

You must remove all paint or anodizing and have bare metal for all Grounding connections

P-Clips are best for Shielded Cable, a saddle clamp will work, both types must clamp the shield tight

Post some photos of inside your Box / Cabinet I can see better what you have to do.