You Do Need power plug adapter while traveling from Guinea-Bissau to Mauritius.

Here is Why You Need An Adapter

The outlet and plug type used in Mauritius are C and G and in Guinea-Bissau is C. This is how they look like.

Guinea-Bissau

In Guinea-Bissau, outlets of type C are in use.

Type C

Mauritius

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

Type C

Type G