SD card not reviewing in my Nikon D3100! Read description?

It says 'SD card not inserted' I tried the SD card with my other camera it still didn't work. I brought it to Blacks where they put it in the picture review machine and the pictures were FINE and still there but won't work in the camera. They told us to format the sd card or 'erase all the data' but it isn't an option on my Nikon, it says it doesn't work with the feature i'm on. Please Help

Added (1). There's a format option on my nikon BUT it won't let me click it. How do i enable it?

Your camera does allow you to format your SD card. Your manual can tell you how to do so. If the pictures are from a different camera, they won't show up on your D3100. Before formatting the card, plug the card into your computer and make sure there aren't any important pictures on it.

How is formatting not an option? It's under menu. Look in your manual. Make sure you got the pictures off the card first if you want them. The pictures are probably worth a lot more to you than the card though so if you salvaged the pictures just toss it and get a new one. If it's acting wonky you probably don't want to take a chance on losing your pictures in the future.

It sounds as if this card is done. I'd suggest you replace it.

SD card didn't work in two cameras. I say throw it away already and buy a new one. Don't forget to format it before using.

http://keerok-photography.blogspot.com/2011/05/how-to-keep-your-memory-card-healthy.html

If Blacks can see your picture, pay them to get the pictures out of the card.