Can I replace a plug with a switch?
Here is one plan for replacing the right hand receptacle with a switch to have a switched light. I think this is correct, but it would be prudent for you to verify it or have someone else here comment in agreement before you make these changes.


Disconnect the three whites from the receptacle and connect the three whites together. They will not be connected to the switch.
Disconnect the black on the upper screw of the receptacle and connect it to one of the contacts on the switch. This will be the switched hot to the light.
Disconnect the two blacks from the lower contact of the receptacle and connect the two together with a short (~6 in) length of black wire (called a pigtail) giving 3 blacks in one wire nut. Connect the other end of the black pigtail to the other contact on the switch. This connects an always hot (line hot) to the other side of the switch.


Note if you get a good quality switch which allows good connection of multiple wires on one contact, then you can dispense with the pigtail and just put the lower two blacks in contacts which connect them to each other, but do NOT use the ordinary backstab connections for this. Do this only if the back connections are secured by screw pressure. (I don't know if there are switches which have this feature, but if there are, it will save room and be easier.

You could put the two blacks under one screw like it evidently is on the receptacle, but it is not recommended to put two wires under one screw unless the device is rated for multiple wires under one contact.