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

Here is Why You Need An Adapter

The outlet and plug type used in Saint Lucia is G and in South Sudan are C and D. This is how they look like.

South Sudan

In South Sudan, outlets of type C and D are in use.

Type C

Type D

Saint Lucia

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

Type G