I dont know where any car auctions are located and I need to buy a car.

My brother has a 2000 Trailblazer and doesn’t have the keyless entry remote for the power locks. He needs to know where in the car the controller is for the keyless entry. He tells me his dad had a 2000 Trailblazer that DID have keyless entry so he’s sure this one came with it too. He wants to remove the old controller so he can buy & install a new one. By the way, are there remote starters that also act as keyless remote? Anyhoo, my main question is where is the controller located? Thanx for any advice!