You Do Need power plug adapter while traveling from Mongolia to Liberia.

Here is Why You Need An Adapter

The outlet and plug type used in Liberia are A, B, C and F and in Mongolia are C and E. This is how they look like.

Mongolia

In Mongolia, outlets of type C and E are in use.

Type C

Type E

Liberia

In Liberia, outlets of type A, B, C and F are in use.

Type A

Type B

Type C

Type F