You Do Need power plug adapter while traveling from Mauritius to Swaziland.

Here is Why You Need An Adapter

The outlet and plug type used in Swaziland is M and in Mauritius are C and G. This is how they look like.

Mauritius

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

Type C

Type G

Swaziland

In Swaziland, outlets of type M are in use.

Type M