You Do Need power plug adapter while traveling from Sierra Leone 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 Sierra Leone are D and G. This is how they look like.

Sierra Leone

In Sierra Leone, outlets of type D and G are in use.

Type D

Type G

New Caledonia

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

Type C

Type F