You Do Need power plug adapter while traveling from Tuvalu 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 Tuvalu is I. This is how they look like.

Tuvalu

In Tuvalu, outlets of type I are in use.

Type I

Puerto Rico

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

Type A

Type B