You Do Need power plug adapter while traveling from Tuvalu 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 Tuvalu is I. This is how they look like.

Tuvalu

In Tuvalu, outlets of type I are in use.

Type I

San Marino

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

Type C

Type F

Type L