How to shoot a noise free video with nikon d3100 at night?

I need camera configurations

You do what the motion picture people do.

You ADD light in a way that emulates night, but is bright enough to shoot using moderate ISO film (sensor settings)

Here is what you can do if you use added light to make it look like it is night time

Unfortunately, many other wise intelligent people never take the time to take classes in film making and make unwarranted assumptions when it comes to shooting video. This includes recording sound, lighting the sets, understanding what kind of computer they need to edit the video and probably have never heard of Foley.

Step 1, buy the fastest lens you can. If you can live with a prime lens (non-zoom) you can go as low as f/1.4. Otherwise the best zoom lenses are f/2.8.

Step 2, keep your ISO as low as you can. Higher ISO results in noise.

The difference between a 50mm f/1.4 and your kit 18-55mm f/3.5~5.6 @ 50mm is 4 stops, and between a f/2.8 and 5.6 is 2 stops.

This is significant. For example, if you normally have to shoot at ISO 3200 on your camera in low light environments, 4 stops means you can dial the ISO down to ISO 200, and with 2 stops, ISO 800.

Again, this comparison assumes you are using your kit lens at 50 or 55mm vs.a f/1.4 prime or a f/2.8 zoom.

While adding some lighting is also a good idea, you can't always do that. However, the combination of lighting and fast lens is the ultimate solution.

There's no such thing as noise free at night.

There are no configurations, your camera image sensor has limits.

Your only options at this point is add light, and add a lens with a large aperture and shoot wide open, or nearly so. You will need a prime lens.

That will allow your camera to shoot at a lower less noisy ISO, but even then that does not mean your images will be free of noise.