Need help need help to install a radio in a chevy s-10 need the right plug?

trying to install a pioneer dep-49001b into a chevy s10 withall the bells & whistles no on star i need to know want plug i need to plug into the one thats in truck i got one at best buy but it was not the right one can anyone tell me the one i need or where to contact to get info. or where to get one