Nikon d7000 memory card?

I have big problem, please Help! I made some photos with 1 memory card in camera, and I saw them on the display. When I came home, and put the card in computer, new photos weren't there, just old ones. And now I can't even see them on the display. What should I do?

Added (1). So, my camera saves in 2 formats, JPEG and NEF. My computer can't open NEF so I delete it every time. It appears that this time all photos were in NEF (I don't know how), and I've deleted it. I don't't even knof what NEF is, and now I'm trying to restore deleted files, but hopeless. It seems impossible… Help please…

Your camera has two memory card slots, you have saved them to both, or checked for a card in the other slot?

*Install the software that came with your camera, it'll enable you to transfer the NEF images over. Once they are over there's a viewer that will allow you to see them, and you can even get a plug in that will enable windows to read them - and all this is going to cost you nothing. If you don't have the original disc, you may need to have your camera plugged into the computer so that the Nikon site can verify that you are a legitimate owner.

NEF is a raw format used by Nikon. You need a program supplied by Nikon to convert NEF to JPEG. It should be on a CD that came with your camera, or you can download it from Nikon (I think the program is View NX).In your manual, set your image format to JPEG (JPG), fine (see page 85 in your manual).

You'll need an undelete utility to get your NEF files back. Or, don't worry about the images you deleted.

You accidently switched the format to RAW
NEF is a type of RAW file, you need photoshop to open that up, or install the software that come with your Nikon.