I bought a 7 way flat to 6 pin round adapter. Then had to take it apart and swap the wire in the adapter to match the trailer for the brakes. That way you can leave the truck wired for which ever standard you want to follow and then adapt plug.
Key is to see if its wired like an RV or either a horse trailer to figure which pin to swap in the adapter. Note I pull a gooseneck and its wired like a horse trailer.