You Do Need power plug adapter while traveling from Montserrat to Saint Vincent and the Grenadines.

Here is Why You Need An Adapter

The outlet and plug type used in Saint Vincent and the Grenadines are A, B and G 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

Saint Vincent and the Grenadines

In Saint Vincent and the Grenadines, outlets of type A, B and G are in use.

Type A

Type B

Type G