You Do Need power plug adapter while traveling from El Salvador to Nepal.

Here is Why You Need An Adapter

The outlet and plug type used in Nepal are C, D and M and in El Salvador are A and B. This is how they look like.

El Salvador

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

Type A

Type B

Nepal

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

Type C

Type D

Type M