You really want to put a motor on a PVC pedal cart??? Do you see how much it flexes? No way it will last any reasonable amount of time and you will end up stranded somewhere with two halfs of a pedal cart lol.
If you really insist, it is just a simple 49cc HS kit - the cheapest version you can get with the terrible chain transmission is around $180 on Amazon but I would highly recommend the one closer to $250 that comes with the much better belt drive transmission. Will have everything you need parts wise besides a way to mount the motor to the frame(comes with a bicycle frame mount, not a normal motor plate) and a way to mount the sprocket to your axle(which I can't even see in the pic so can't help much there).