You Do Need power plug adapter while traveling from Kiribati to Guatemala.

Here is Why You Need An Adapter

The outlet and plug type used in Guatemala are A and B and in Kiribati is I. This is how they look like.

Kiribati

In Kiribati, outlets of type I are in use.

Type I

Guatemala

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

Type A

Type B