Need to find my iCloud account?

So basically I lived in South America for a pretty long time and I took TONS of pictures with my iPhone over there. I was out one night and I guess I must've gotten that phone stolen. So I got my old iphone back and got that iCloud account but then realized my old phone had a different account. Tried calling Apple but they only knew how to back up the iCloud account I don't need but they said if I could get the serial number of that old phone they could find out what was my old account. I called my carrier, At&t, and they didn't have it. I took hundreds of pictures and now I have NONE, it's very important to me to get those back. Any help would be greatly appreciated.

If you Don't Remember your icloud Account Info Than your Not Gonna be Able to Get Back to it