You Do Need power plug adapter while traveling from Cameroon 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 Cameroon are C and E. This is how they look like.

Cameroon

In Cameroon, 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