it actually wouldn’t be that hard to work out. You just need the rocket equation (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation) to give an estimate of the mass of fuel.
You just need to know the delta V(which is known for transit to Pluto), the specific impulse of the engine, which is know after you select your rocket, and the mass of the rocket without fuel, which is also known. You just rearrange to work out the fuel mass. You can experiment with different engines (chemical, ion) to see how they affect the amount of fuel needed