Trying to follow along Cloud Wolf's gun tutorial series

Currently I have done a few of the things that he did in his playlist, but I have recently gone back and started from scratch. At this time, I am struggling to update his right click detection to 1.21.4 . I would also be interested in knowing is there is a way to convert commands made for one version to commands for a newer version(1.19 to 1.21.4 for example) Any help here is appreciated. Link: https://www.youtube.com/watch?v=ufD4eY0mWII&list=PLTRX9BDGoc4fBc-CpSGtHt5URDvudB7fk&index=2