What is the mirror of the compound microscope?
A compound microscope can either have a light bulb or a mirror. If your microscope has a mirror then you might need a light source to point at the mirror to view your slide. You could use a flashlight as a light source. If yours has a light bulb, turn it on to view your slide. You can’t use the light in your room or lab to view your slide, because you will block all that light when you use the microscope.