You Do Need power plug adapter while traveling from Andorra to Saint Lucia.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Lucia is G and in Andorra are C and F. This is how they look like.

Andorra

In Andorra, outlets of type C and F are in use.

Type C

Type F

Saint Lucia

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

Type G