You Do Need power plug adapter while traveling from Mongolia to Isle of Man.

Here is Why You Need An Adapter

The outlet and plug type used in Isle of Man are C and G 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

Isle of Man

In Isle of Man, outlets of type C and G are in use.

Type C

Type G