You Do Need power plug adapter while traveling from Saint Lucia 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 Saint Lucia is G. This is how they look like.

Saint Lucia

In Saint Lucia, outlets of type G are in use.

Type G

San Marino

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

Type C

Type F

Type L