You should be able to check the small print on an electrical device or power adapter to see if it's dual voltage or not.
If you see 100-240V 50/60Hz printed on the device or power adapter,
it is dual voltage and will work with all voltages and frequencies used worldwide.
If you can't find this information on the device or power adapter itself,
you can maybe find it in the manual or by contacting the manufacturer of the device.