How to increase the shutter speed on Nikon d3100?

I want to take pictures of fast moving objects (sports)

Thats the number that says 1/### or #"

One of the scroll wheels should change that

Read the manual that came with the camera and/or take a photography course.

Look on page 75 and 77 of your user manual.

Your last two questions are answered in your user manual.

Did you lose it?

The following would help.

1. Use a fast lens
2. Stay in a place with enough lights
3. Use high ISO or AUTO ISO
4. Use aperture priority (A) and F number at the lowest possible

Read
The
Frickin
Manual

To increase the shutter speed, turn the dial on the top of the camera (near the shutter release button) to S, then rotate the command wheel which is on the back of the camera (upper right). You should see the shutter speed on the display screen and in the viewfinder.