You Do Need power plug adapter while traveling from Saint Barthélemy 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 Saint Barthélemy are C and E. This is how they look like.

Saint Barthélemy

In Saint Barthélemy, outlets of type C and E are in use.

Type C

Type E

Sierra Leone

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

Type D

Type G