You Do Need power plug adapter while traveling from Mauritania 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 Mauritania is C. This is how they look like.

Mauritania

In Mauritania, outlets of type C are in use.

Type C

Isle of Man

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

Type C

Type G