You Do Need power plug adapter while traveling from Guinea to Congo.

Here is Why You Need An Adapter

The outlet and plug type used in Congo are C, D and E and in Guinea are C, F and K. This is how they look like.

Guinea

In Guinea, outlets of type C, F and K are in use.

Type C

Type F

Type K

Congo

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

Type C

Type D

Type E