How to upload pictures to computer with nikon d3100?

I have a usb cord for it that fits and everything but it didn't come with it. When i connect it to the computer it doesn't show up on the computer. I was wondering if i have to do something extra for it to show up like mess with the settings or what not.

Don't bother with cables or special software!

The easiest and best method to transfer photos and video from your camera to your computer is via a little USB card reader (which are very cheap these days and widely available).

Card readers also work for moving photos from the computer onto a card (in case you want to take a few photos to get printed - NOT for viewing on the camera purposes).

Plug the reader into a USB port and insert the memory card.
It will show up as a drive, and you can simply drag and drop the photos across to the folder of your choice.
http://www.ephotozine.com/article/Card-Readers-explained-140

Oh and… Do read your manual!

You don't say if you're following the procedure in your manual. For instance, are you turning your camera on after you connect the cable?