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

Here is Why You Need An Adapter

The outlet and plug type used in Cape Verde are C and F 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

Cape Verde

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

Type C

Type F