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

Here is Why You Need An Adapter

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

Micronesia

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

Type A

Type B

Kiribati

In Kiribati, outlets of type I are in use.

Type I