I burned a potato in the microwave,,now I have a awful smell .

Wipe it out with some vinegar. See if that does it.

Put a small dish of baking soda in the MW, close the door and let it sit several days. Baking Soda will absorb the odors.

Wipe down inside with a baking soda/vinegar mix. Follow up with fresh halved lemon wipe.

Try scrubbing with baking soda and then microwaving a bowl of vinegar and water.

A bowl of coffee grounds, fresh I believe, will also absorb the smell.

https://www.hometalk.com/diy/clean/microwaves/how-to-steam-clean-the-microwave-2353782

Fill a bowl with 1/2 cup water and 1 tablespoon white vinegar.

1. Microwave it for 4-5 minutes and leave it with the door shut for 10-15 minutes.
2. Steam will loosen smell-causing detritus stuck to the walls. ...

After the waiting period, remove the bowl and wipe the inside of the microwave down with a paper towel.