You Do Need power plug adapter while traveling from Saint Helena to New Caledonia.

Here is Why You Need An Adapter

The outlet and plug type used in New Caledonia are C and F and in Saint Helena is G. This is how they look like.

In Saint Helena, outlets of type G are in use.

Type G

In New Caledonia, outlets of type C and F are in use.

Type C

Type F

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