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

Here is Why You Need An Adapter

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

Guyana

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

Type A

Type B

Type D

Type G

Sri Lanka

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

Type G