Well, first your system needs to be on version 9.2 or older. If it's the case, you may install a CFW (following this guide:
https://gbatemp.net/threads/wip-complete-custom-firmware-guide.396349/), create your emuNAND, and then change its region (with this guide:
https://gbatemp.net/threads/guide-change-emunand-region.392099/). I don't think it is possible to change the region of your sysNAND (with softmodding, you can do it with hardmodding but it's really difficult and risky from what I've seen)
If your 3DS is on 9.3 or newer, you can only hope for a new kernel exploit to be released though.