What kind of Xbox 360 do I have?

I've been having an Xbox 360 for a few years. I got it in 2009, and it has never broken down, or anything. But I've been reading about Xbox's, and I've heard of two kinds: the 4 GB and the 250 GB. But I don't think I have either. The 4 GB should have FOUR GIGABYTES of space on it! And the 250 GB should have 250 GIGABYTES! But mine has neither. Mine only holds about 200 MB of storage. I repeat: 200 MB. It is not nearly enough. I constantly have to delete my saved games because they take up too much space and I can't play anything else. Mafia 2 takes up 51 MB, so does Minecraft. A ton of the games I have take up all the space. If it is a 4 GB, shouldn't it have MUCH more space? Same with the 250 GB. I'm so confused. My Xbox is white, and I'm not sure if it's a slim or not. What is it, and how can I fix this storage problem? Can I buy a hard drive for it? What about a USB? What do I do? What is my Xbox? Thanks.

P.S. I don't have Xbox Live. I never have.

You have a 2009 model either falcon or jasper
and no hard drive from the sound of it you have a memory card

no its not a slim

yes you can buy an hard drive for it
20 gig http://www.amazon.com/...000B6ML32/
or 320 gig
http://www.amazon.com/...00656HLGO/
and you can plug a usb stick in it the xbox wil want to format it and you can only use it with the xbox

I have wite xbox 359