You Do Need power plug adapter while traveling from South Korea to French Guiana.

Here is Why You Need An Adapter

The outlet and plug type used in French Guiana are C, D and E and in South Korea is F. This is how they look like.

South Korea

In South Korea, outlets of type F are in use.

Type F

French Guiana

In French Guiana, outlets of type C, D and E are in use.

Type C

Type D

Type E