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

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L and in Sweden are C and F. This is how they look like.

Sweden

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

Type C

Type F

Eritrea

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

Type C

Type L