You Do Need power plug adapter while traveling from Namibia to San Marino.

Here is Why You Need An Adapter

The outlet and plug type used in San Marino are C, F and L and in Namibia are D and M. This is how they look like.

Namibia

In Namibia, outlets of type D and M are in use.

Type D

Type M

San Marino

In San Marino, outlets of type C, F and L are in use.

Type C

Type F

Type L