How to get out of this mode on nikon d3100?

As the title says

Use the 4-way button to switch between visual modes.

This should not be a problem since it is not necessary to look at the LCD after each shot if you have taken the time to learn the fundamentals of photography and how to use the features on your camera.

You can learn to balance ISO, shutter speed and lens aperture here.

http://camerasim.com/apps/camera-simulator/

Your user manual is going to be the first place to look when it comes to using your fine camera.

What mode? Your camera is in Auto mode. Turn the mode dial to something else.

You mean the status (all those numbers and thing-a-lings) during preview? Consult the manual on how to keep it simple. It's just one button (usually Info) but since I don't use Nikon, I don't know exactly what it is with yours. You can try the last one on the left side (labeled with an "i") and keep pressing until you see what you like.

Nice green display! I didn't know Nikon made an effort to look pretty nowadays.

Photo Information is covered on page 100 of your manual. Hint: press the up or down of the multi selector button.