You Do Need power plug adapter while traveling from Saint Kitts and Nevis to Puerto Rico.

Here is Why You Need An Adapter

The outlet and plug type used in Puerto Rico are A and B and in Saint Kitts and Nevis are D and G. This is how they look like.

Saint Kitts and Nevis

In Saint Kitts and Nevis, outlets of type D and G are in use.

Type D

Type G

Puerto Rico

In Puerto Rico, outlets of type A and B are in use.

Type A

Type B