You Do Need power plug adapter while traveling from Portugal to Belize.

Here is Why You Need An Adapter

The outlet and plug type used in Belize are A, B and G 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

Belize

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

Type A

Type B

Type G