You Do Need power plug adapter while traveling from Sri Lanka to Sint Maarten.

Here is Why You Need An Adapter

The outlet and plug type used in Sint Maarten are A and B and in Sri Lanka is G. This is how they look like.

Sri Lanka

In Sri Lanka, outlets of type G are in use.

Type G

Sint Maarten

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

Type A

Type B