What wireless transmitter/receiver do I get?

I have the Nikon d3200, and I just bought the Olympus lapel mics. I bought a transmitter/receiver but it didn't fit into my camera. It's a 3.5mm stereo jack.

Which should I buy? I need this to do artist interviews.

Also- how do I set up more than one microphone with these transmitters?

Go to a proper camera or electronics store and have them make (or perhaps you can buy) an adaptor to take you plug down to the proper size… As long as your receiver is putting out mike level audio you don't need a new receiver but you do need a new plug.