You Do Need power plug adapter while traveling from Côte d'Ivoire (Ivory Coast) to Saint Helena.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Helena is G and in Côte d'Ivoire (Ivory Coast) are C and E. This is how they look like.

Côte d'Ivoire (Ivory Coast)

In Côte d'Ivoire (Ivory Coast), 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