I have an 1989 Chevy cheyenne standard cab and was wondering if someone could tell me what part or parts I need to repair the floor under the sill plate that rusted out where stll plate screws to.Need to know if I need a rocker panel or a floor pan because it is hard to tell from pictures on parts websites what I need.I t is only rusted about 1/2" wide on 2 of the screws where it screws down

Thanks in advance