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

Here is Why You Need An Adapter

The outlet and plug type used in Sint Maarten are A and B 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

Sint Maarten

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

Type A

Type B