You Do Need power plug adapter while traveling from Solomon Islands to Bhutan.

Here is Why You Need An Adapter

The outlet and plug type used in Bhutan are C, D and G and in Solomon Islands are G and I. This is how they look like.

Solomon Islands

In Solomon Islands, outlets of type G and I are in use.

Type G

Type I

Bhutan

In Bhutan, outlets of type C, D and G are in use.

Type C

Type D

Type G