Carnival cabin outlets, by ship class.

Carnival's official FAQ tells you exactly which ships have USB and which don't — the line publishes its per-ship table, and you should treat it as ground truth. Power strips and multi-plug adapters are allowed as long as they're non-surge. The catch is the older hulls: Dream, Magic, Breeze, and the surviving Conquest-class ships have a single usable AC outlet per cabin and zero built-in USB on their original blueprints.