This is a common and simple conversion.
1. Replace the 2 pole 30amp breaker with a 2 pole 20. You will only use one pole but I hate panel blank "fillers" They always fall out
2. Replace the 240V receptacle with a 120V recep. The existing #10 wire will wrap arouind the terminals but it will be a bit difficult to manuver. Use black and white for the hot and neutral (hot = brass screw, neutral = silver screw). Bare ground goes to the green ground screw. Cap the extra red wire with a wirenut.
The last thing is to decide how to deal with mounting the recep and the cover plate. I would do whatever is easy.
2 gang box? Install a second recep and a double duplex cover plate or find a specialty duplex/blank plate.
4s box with a 2 gang mud ring? Same as above or change the mud ring to single gang and patch the sides.
I gang mud ring? Simply install the recep and cover plate.