At the sake of sounding like an Uber Geek, there are 1073741824 bytes one Gigabyte but with formatting, you loose some data which is why drives and cards etc don't ever format to the size on the box.

A couple of things to consider with your card - is it formatted to the device? If not not sure how you would do that (think camera formatting there's likely to be a menu option) and / or do you have a known working SD card? Is it for SD or HD cards (yes, there's a difference) also check the data speed, a slow card might not work (HD cards tend to be faster).

Have a read of the destructions that came with the cam - it should have an indication of what to buy.