Sockets & plugs
Guyana uses 120/240V, 60Hz with sockets and plugs Type A, Type B, Type D and Type G.
Type A
Type B
Type D
Type G
Adapters and transformers
Sockets & plugs
You may need an adapter while in Guyana.
Frequency
Frequency difference is generally not a problem - almost all items (except some types of clocks) will work on both and you shouldn't worry about it.
Voltage
If there is a voltage difference between countries, you probably won't need a transformer/converter if you use recent devices and appliances because they all work worldwide automatically.