hello!
In your gear dilemma, you will need to consider TORQUE, a measure of strength of pull. If you
"gear down" a motor, the torque will increase, but the speed decreases. If you "gear up"
a motor, the torque will decrease, and the speed will increase; assuming the motor parameters
stay constant. This is not rocket science, but attention to detail is required.
There may be MANY gear calculators online, for sure. The trick, again, is to recognize
the power/speed that you want to work with.
I would recommend getting your speeds and torques done with a online calculator, then
you can see what is available from stores.
Good Luck!