Compatibility summary
You will need a travel adapter in Guyana; plug types used there differ from South Africa.
Plug comparison
South Africa plug types: C D M N
Guyana plug types: A B
There is no common plug type between South Africa (C D M N) and Guyana (A B). You need a travel adapter.
Voltage comparison
South Africa: 230V, 50Hz
Guyana: 220V, 50Hz
Voltage difference is within a range many devices tolerate; check your appliance label.