What you're looking for is the receiver. They're normally mounted to the floor under a cabinet relatively close to the main CB/Fuse panel. It looks like this:
'04 K3500 Silverado LS with LS3 Connect & Cruise- with Intimidator SSI PKG- Reprogrammed 4L80E
2016 Salem 27RKSS
1984 CHEV SCOTTSDALE K20 2GCGK24J0E1XXXXXX (Chevrolet Legends-Class of 2019)
"...exhaust fluid? We don't need no stinkin' exhaust fluid"