You Do Need power plug adapter while traveling from Sierra Leone 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 Sierra Leone are D and G. This is how they look like.

Sierra Leone

In Sierra Leone, outlets of type D and G are in use.

Type D

Type G

San Marino

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

Type C

Type F

Type L