The plug itself does not indicate compatibility. For example, the US and Japan both use the same plug shapes for electronics, but Japan is a clusterduck as far as what electricity they use, so US devices may not work in a Japanese socket.
There's two things you need to know about whether or not it's safe to use electronics from one country in another:
- What frequency it uses. It's either going to be 50Hz, 60Hz, or both (Japan uses 50Hz in some parts, 60 Hz in others)
- What voltage it uses. This is a range from 100V-125V and 220V-240V.
Generally speaking:
- North American countries (mainly Canada, Mexico, the US, and the Caribbeans)use 110-120V 60Hz electricity
- Europe, Asia (with the exception of some East/Southeast Asian countries), Africa, Australia, and some of South America use 220-240V 50Hz
- The rest of the world is a mishmash of either frequency and voltage range.
Refer to this map:
https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/World_Map_of_Mains_Voltages_and_Frequencies,_Detailed.svg/2754px-World_Map_of_Mains_Voltages_and_Frequencies,_Detailed.svg.png
So to figure out whether or not the electronics are compatible in the first place, look at the label on the power brick (if it has one) or near the electricity input. It should say what frequency and voltage it uses. As for how much current it uses, this isn't something to generally worry about. If you exceed the limit on the circuit, it usually trips a breaker or blows a fuse. And if the socket specifically cannot provide the normal amounts of current, it should clearly say how much it can.
Otherwise, if your electronics are universal, you just need a passive converter.
However, make sure if your plug has a ground pin that the converter also converts the ground pin. If your electronics take only one frequency and voltage, you need to get an active adapter. Note that active adapters have a power limit. Smaller ones are only good for phone chargers, and maybe up to a laptop.