how to track conversions?

I have a site www[dot]videogamesrental[dot]net It reviews three video game online rental sites and uses cj for one and another program for another. I have a ppc campaign but have no idea which keywords are converting and which aren’t. I don’t know how to track them since all ppc clicks go to the homepage and then from there, go to the affiliate site and make a sale. Any help would be greatly appreciated.

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