How many GB does my Xbox 360 have???

Hello,

It depends on the model of your Xbox 360. Is it a premium, an arcade, or an elite?

The difference can be seen in the aesthetics.. The premium is slim, and the disc drive (the part that opens and closes to insert the disc) is metallic gray.
The arcade is wider than the premium, and its drive is white, blending in with the color of the Xbox 360.
And the elite is a bit smaller but just as wide as the arcade, though I believe it's only available in black..
So is it a premium or an arcade?

Well, you must still know which Xbox you bought, right?

I no longer have the original box.

I have the same problem but I don't have the box, what should I do?

Go to system settings>storage

You look at the purchase box...