Ender extender issues

Hello every one… I am sorry but i am not good at all with coding… it looks chinese to me lol Im asking for a hand here, i have an ender 3 pro with Bltouch and creality silent board 4.2.7, i recently installed the ender extender 400x400mm kit and i have a custom height of 730mm my issue is its still thinking it has the stock or original bed. Can someone please explain how i can change the bed sizes without needing to code? or if someone can link me or point me to someone who already has something like this done or firmware that already has this done i dont mind loosing some height if need be but i just wanna be able to use the whole print bed thanks