Step up 3.7 volts to 9v

:confused: I really want to Step up 3.7 (2 Ah) to 9v or 12v for my motor drive. How to I do that using mosfets? or anything except ics?

How many amps (or milliamps) does your motor require?

Making a DC to DC voltage boost circuit is not simple. Just buy one.

Or change to low-voltage motors.

...R

As I know at least 500 mah, maybe at least 250 mah for a 30 min drive

Kinorter:
As I know at least 500 mah, maybe at least 250 mah for a 30 min drive

It is important to learn the difference between mAh and mA. Your step-up converter will need to be able to produce enough mA.

How many mA does your motor draw {A} in normal use and {B} when stalled?

...R

Step-up converters (commonly called boost converters) are really cheap - 2A ones can be had for a few USD equivalent. It's not worth trying to make your own.

The circuits are quite simple, but you will need a proper PCB for stability, especially if you go for higher currents.

You will not have much current to work with. You need to get more cells.

If voltage is pressure, increasing voltage is like putting your thumb over an open garden hose to make the water shoot farther/faster. The same amount of water is available. Your motors need more water and you can't thumb a hose and create water.