I am reinstalling an entire stereo system that was in my truck but came out because I was going to sell it and ended up not selling it. Anyway, I have all the speakers, amps, and wires ran. Now that im installing the headunit Ive come to a problem. The little plug that goes into the back of the headunit and goes to a big male end wiring hardness is whats confusing me. I have that male end plug, and then the other big plug that is ran to the amps is the other big plug I have which is also male end. I dont remember an adapter being between the two, and I cant find the female end plug under my dash anywhere. help is greatly appreciated.

The plug on the left in my hand is the one plugging into the headunit, the one on the right runs back and plugs into the amp powering the door speakers.

Does one of them have to plug into somewhere pre existing in the truck that feeds power?