You Do Need power plug adapter while traveling from Montserrat to Tunisia.

Here is Why You Need An Adapter

The outlet and plug type used in Tunisia are C and E and in Montserrat are A and B. This is how they look like.

Montserrat

In Montserrat, outlets of type A and B are in use.

Type A

Type B

Tunisia

In Tunisia, outlets of type C and E are in use.

Type C

Type E