You Do Need power plug adapter while traveling from Rwanda to Guam.

Here is Why You Need An Adapter

The outlet and plug type used in Guam are A and B and in Rwanda are C, E, F and G. This is how they look like.

Rwanda

In Rwanda, outlets of type C, E, F and G are in use.

Type C

Type E

Type F

Type G

Guam

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

Type A

Type B