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

Here is Why You Need An Adapter

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

Oman

In Oman, outlets of type G are in use.

Type G

Nepal

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

Type C

Type D

Type M