If you want to move your stuff to a bike with 26" wheels, you'll need to stick with a 24v battery because your motor will spin too fast at 36v. A 36v battery will make the motor try and spin 50% faster, and then the 26" wheels will add 30% speed to that, which makes 95% faster. It won't have enough power to run at that speed, so everything will get very hot.
All these things are simple, but end up complicated. If you put a 36v battery on your present bike, you'll need a throttle, a new controller with panel and a new pedal sensor to match the new controller. Inevitably, there will be wiring issues that require soldering and swapping pins in the connectors. When you've done all that, your gearing will be too low, so you'll need to change the gearing, which means a new difficult to find free-wheel gearset or a larger chainwheel. Both these things require special tools.
You can get more power from your present bike by opening the controller (seven screws - 4 on the wires end and 3 on the side) and adding solder to the shunt like in those two threads that I linked to. If you transferred your stuff to a 26" wheel bike, that procedure would be necessary because your motor doesn't make much torque at the moment because the controller won't give it much current.
