You Do Need power plug adapter while traveling from Burkina Faso to Saint Helena.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Helena is G and in Burkina Faso are C and E. This is how they look like.

Burkina Faso

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

Type C

Type E

Saint Helena

In Saint Helena, outlets of type G are in use.

Type G