You’ll need a potential divider to do it badly or a PWM to do it better. If you’re asking how to do this I think you might be better off buying a fan and controller combined
An alternative to speed control is to run full speed and vent off some of the blown air in some way, but that may not be suitable for what you are using it for.
Are those PWM controllers suitable for a brushless motor, which uses a stepper motor configuration and there could be conflict between the PWM and the stepping frequency?