Well to convert a "gateway/arcode" to "ntr" code you need to understand what the GW/AR code does.
You can get an idea with the references at http://www.maxconsole.com/maxcon_forums/threads/293144-Gateway-ARCode-Cheat-Sheet
Once you understand what the code does, it's time to code some lines to simulate the behaviour the gw/ar code does.
It's going to be tough if you don't know how to code in C but if you know, it's going to be a lot easier.
You can also find more info about it in this thread I made in gbatemp: https://gbatemp.net/threads/how-to-find-pointers-on-ntr-debugger-memory-dumps-ntr-cfw.415995/
Hope that helps
