Look for an aluminum tag--or a silver or white adhesive label. The model number may be printed or stamped onto the tag and it may be written in two different type sizes or styles.
Built In
On the face frame, or the side of the control panel with the door open.
On the bottom of the unit.
Free Standing
Free-Standing With the door open, mounted to the door jamb near the control panel.
Mounted on the rear of the microwave.