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

Here is Why You Need An Adapter

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

Eritrea

In Eritrea, outlets of type C and L are in use.

Type C

Type L

Congo

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

Type C

Type D

Type E