How to tell how many GB my iPhone 4S has?

My friend sent me an iPhone 4S from abroad and I don't know how many GB it has. I know you can tell by going to Settings, but this phone has no SIM card so it won't let me access its menu. I tried setting it up but after selecting language, timezone and Wi-Fi connection it stops me saying there's no SIM card. So I'm also wondering if I can put my own SIM card into this phone for a minute, check its capacity and then put it back on my own phone (I have an iPhone 4S too). But the thing is I don't know how to remove my SIM card from my phone, Can anyone tell me how to find out the GB capacity without having to check it on Settings? Or at least tell me how to switch my SIM card from one phone to the other?

Settings, general, about then it say capacity

It doesn't need a sim card to access its menu. Just go to settings app, general and then about and it should be there.

So are you saying that it won't let you go through the menu screen like the home screen if yes i guess your phone is locked and you need to unlock it correct me if i'm wrong