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

Here is Why You Need An Adapter

The outlet and plug type used in Eritrea are C and L and in Sri Lanka is G. This is how they look like.

Sri Lanka

In Sri Lanka, outlets of type G are in use.

Type G

Eritrea

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

Type C

Type L