What Mode should i put my nikon D3100 on to take pictures of fireworks

What Mode should i put my nikon D3100 on to take pictures of fireworks?

Camera on tripod pointing where the display will be. There will be nothing for the auto focus to lock onto, so manual focus, on, or close to infinity. Shutter on 'B' setting with a cable release, aperture around f11 and an ISO of 100.

Wait for the fireworks and trip shutter, hold it open and let the fireworks 'paint their light' onto your film. Close the shutter - repeat. This bit needs practise.

It's exactly the same technique as 'painting with light'.

The idea is that with the aperture/ISO you have set and pointing at a black sky the sensor records nothing, until a firework appears and paints it's light onto your film.

Everything Screwdriver said, but I would add that you should make sure the autofocus is turned off and you manually focus to infinity.