You Do Need power plug adapter while traveling from Sint Maarten to Sierra Leone.

Here is Why You Need An Adapter

The outlet and plug type used in Sierra Leone are D and G and in Sint Maarten are A and B. This is how they look like.

Sint Maarten

In Sint Maarten, outlets of type A and B are in use.

Type A

Type B

Sierra Leone

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

Type D

Type G