However, use of these plugs without a transformer or voltage converter can result in fireworks. The voltage in Europe is twice that of the voltage in the United States, and while many electronics are designed to adapt to voltage changes, it is crucial to check. If the device is not capable of handling 220 volts of electricity, it will fail.
By the time the ducklings are 3-5 weeks old, weather-dependent, they can spend warm, sunny days outside, carefully supervised and protected from predators. Until the ducks are fully feathered around 7-9 weeks old, they have trouble regulating their body temperature and need heat.
I would let them get a two or three weeks older before you let them live at the pond. They will be able to take better care of themselves then. Just be sure to check on them often when you put them at the pond. Most domestic ducks can't fly very far. Some can't fly at all.