About the Canon SX30 IS how to ZOOM?

I know it's a STUPID question… But how do you zoom? With a button? Or by moving the Lens with your hand?
And, is it a good camara?
If i bought a 3100D nikon with a lense of 18-55 and didn't change it, which camara would be better and why? The 3100D nikon, of the SX30 Canon?

They use a rocker switch.

Canon SX30 IS has 35x zooming

Canon PowerShot SX30 IS sports ultrasupermega 35x zoom.