Problem with my Nikon D3100 focusing?

When I try to take a picture using the digital focus, it will not take the picture! It takes the picture but not zoomed in it only uses the optical… That's not the case with my L120. The way it looks in the live view is the way it captures the picture.am i doing something wrong. I'm new to dslr.

Using a DSLR is really quite a bit different than using a bridge model like the Coolpix L120. The L120 has buttons that control the zooming. On a DSLR, YOU control the zoom with a ring on the lens.

Both your camera and lens should have come with an instruction manual; if you look in the one that came with your lens, it has a diagram that will show you exactly where that ring is located. If you don't have the manual, the ring probably has numbers on it that range from 18 to 55. Turning it to the right will zoom in, while turning to the left will zoom out.

The way you worded this question was a little confusing. If you are, in fact, having trouble with the autofocus on your camera and not the zoom, you should make sure that the selectors on both the camera and lens are set to AF rather than M.

Have fun with your new camera!

When the camera prevents you from taking the photo, it's because you are not properly focused.

Autofocus systems are not perfect. In low light situations, when there's little contrast in the photo, or if you are too close, autofocusing may not work.

I don't understand your second sentence.