2000 Camry: Side rearview mirror broken

There is a cover on the inside that snaps in place. This cover will be the same shape as the footprint of the mirror where it attaches to the door.

Use an appropriate pry-tool to pop the cover and expose the nuts underneath that hold the mirror on. There are typically three nuts, but I don't know if your Camry has three, or used a clip and one nut. Just take the nuts off that you find and be prepared to catch the mirror before it hits the ground.

Your local junk yard should have a used mirror for your car.