You Do Need power plug adapter while traveling from Portugal 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 Portugal are C and F. This is how they look like.

Portugal

In Portugal, outlets of type C and F are in use.

Type C

Type F

Sint Maarten

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

Type A

Type B