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

Here is Why You Need An Adapter

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

Nepal

In Nepal, outlets of type C, D and M are in use.

Type C

Type D

Type M

Solomon Islands

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

Type G

Type I