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

Here is Why You Need An Adapter

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

Guyana

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

Type A

Type B

Type D

Type G