You Do Need power plug adapter while traveling from Saint Martin to Vatican City.

Here is Why You Need An Adapter

The outlet and plug type used in Vatican City are C, F and L and in Saint Martin are C and E. This is how they look like.

Saint Martin

In Saint Martin, outlets of type C and E are in use.

Type C

Type E

Vatican City

In Vatican City, outlets of type C, F and L are in use.

Type C

Type F

Type L