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

Here is Why You Need An Adapter

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

Greece

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

Type C

Type F

Congo

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

Type C

Type D

Type E