When upgrading the electrical system from 24V to 36V typically the motor, controller, throttle (if it has a battery indicator on it), battery pack, and battery charger need to be replaced.
However, some people choose to over-Volt their 24 Volt motor to make it run faster and in this case, the original 24 Volt motor is reused. Over-Volting a motor can cause it to overheat and burn out so we are not suggesting doing this, however, it is an option that is often exercised.
If you don't mind us asking. What are your goals for the modification? More uphill power, more speed, longer riding time, or???
Here are gear ratio calculation results showing the 10 MPH speed with the original motor and the new 16 MPH speed with a larger motor and smaller wheel sprocket.
A kit such as item # KIT-102 could be used to upgrade the bike to 250 Watts: https://electricscooterparts.com/electric-scooter-kit-102.html
The 65 tooth sprocket that fits the Pulse EM-1000 dirt bike is item # SPT-2565S which is sold on this page: https://electricscooterparts.com/sprockets25chain-wheel.html
We could make a new variation of KIT-102 if you would like any changes made to it such as different; batteries, throttle, switch, etc. And we could also add the 65 tooth sprocket to a variation of the kit.
Please let us know if you have any questions.