I can change dimension units while doing part drawing using prepare option but when I'm using sketch prepare option is not available to change dimension, how to change dimension in Sketch? Please tell me
You can't change the units in the sketch mode. If you create the sketch inside of a model the sketch will take the 3D model units. If you do a stand alone sketch will be just values not units. If you add that sketch in a 3D model later, the sketch will take the 3D model units.