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

Here is Why You Need An Adapter

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

Saint Helena

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

Type G

Côte d'Ivoire (Ivory Coast)

In Côte d'Ivoire (Ivory Coast), outlets of type C and E are in use.

Type C

Type E