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

Here is Why You Need An Adapter

The outlet and plug type used in Tahiti are C and E 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

Tahiti

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

Type C

Type E