206+ rear speakers

The rear speakers were wasted when friends disassembled the tape. It was previously connected to the cable between the ISo socket and the tape socket from the outside. I will connect them to the original tape socket for now, but first I need to connect what and where. And what's the probability that it won't sound when I connect it? Because sometime in the back door when there were no speakers, the friends who had it installed went to the service and opened it.