Change the pilot pressure hoses that run from joysticks done to the control, swap these at the valves. Remove the floor plate(s) to see the valve stack. Boom vavle is closest to the Right Hand travel valve and Dipper Arm is next to the LH travel valve. Move the small pilot pressure hoses from boom to arm and while doing this they must be swapped in an X parrtern (the hose from rear of Arm goes to front of boom valve and that boom from boom goes to rear of arm. Do same for other 2 hoses.
This for earlier models that did not have a selector valve. I'm not sure when the ISO/SAE selector valve was added but it it has one it would be under the seat by your Right foot.