In the webside of pololu num 2294 write that the stepmotor works with 6.3V ,but in the datasheet write that he works with 24V.
you can help me ?
The voltage rating of a stepper motor is not really relevant. It is the current rating that is important, and for that stepper it is 300 mA per winding, maximum.
You can drive that motor with a DC voltage of 6.3V, which will result in 300 mA per winding through the 21 Ohm coils.
Otherwise, you can use a higher DC voltage (for higher step rates) but that requires a current limiting stepper motor driver, like the A4988. You must set the driver current limit to 300 mA per winding or less.