Welcome to the forum!
First thing, be very careful to observe correct polarity when connecting the radio, two red leads are an extremely bad idea.
you should at the minimum wrap some black tape around the negative wire of that power harness. which connects to a 13.8 volt DC source.
The Mic is a 5 pin Din, not sure if radio shack still sells mics, but you could give them a call, I think most of the 5 pin din shack radios are commonly wired.
As for the antenna, you will need one made for CB. the hole on the side is for mounting screws. On the rear of the radio you have the large antenna connection, and most likely two small jacks labeled "PA" and "EXT Spkr" both are audio out connections, one for a Public Address Speaker, the other for an External Speaker (the radio has one built in). and if functional any connections on the rear of the radio except antenna and power are optional.
That corrosion on the radio is slightly worrisome, Not sure how much I would invest in mikes, etc without checking it out first.
Your best bet would probably be to get a little free advise from a local CB shop if you have one, they should also be able to set you up with an inexpensive antenna, and a mike for the radio, after a quick check to see if it actually works.
Alternatively a wanted post on the forum, maybe a mic, and/or antenna might net you a very low investment.
