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

Here is Why You Need An Adapter

The outlet and plug type used in Nepal are C, D and M 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

Nepal

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

Type C

Type D

Type M