how to run a high voltage motor with low voltage Answered

The boxy shaped, widely used, 9V battery is weak sauce.

I humbly recommend replacing it with a stack of 8 AA batteries, and battery holder(s) for the same, for to supply 12 volts for your 12 VDC motor.

I think that is the best, easiest, way to supply power to your motor.

https://en.wikipedia.org/wiki/Nine-volt_battery

Indicates a primary alkaline battery can supply 565 ma for one hour which is slightly over a half ampere and will run a suitably small fractional horsepower DC motor at a lower speed.

You motor consumes power this is the voltage x the current. the result is in watts.

IF you mean the square 9 volt battery - look up the spec sheet for it and you will find it can provide 600 m amps for an hour. that's 0.006 amps. This is FAR less than your motor needs.

No matter what you do the power available remains constant. Otherwise you could get energy for nothing!

There is no way you can power a decent motor with a 9V battery, at least not for more than a few minutes.
And if you use step up converters or similar the result would be even worse.