I think you should still be able to set up OoThax, since your 3DS seems to able to run homebrew fine. If you can get OoThax set up, you should be able to follow the steps from that thread.
Hey question umm on modchipcentral while checking out my payment methods say for usa USA/U.K/INTERNATIONAL (VISA/MASTERCARD). so I think this means I can use a regular prepaid card that isn't international. If so should I just buy a hundred dollar prepaid card or should I just go on and get a international prepaid one.