My appliances are new enough that they will take the 240 volts. I can get a plug adapter for $1 but what will I need to change the Hz?
It will say it accepts 240 V 50 Hz on the device somewhere or on the charger.
You would be better off selling your 60 Hz appliances and buying 50 Hz appliances with electric motors. Fequency converters are not cheap.
The Danger of Running 60Hz Motor on 50Hz Power Supply
Severe heating, no-load current increasing
The power and rotation speed decrease
Starting current increase rapidly, easy to overload
Designed torque severely damage
Significantly shorten the life of the motor
Assuming you are talking about things like phones, tablets, and in my case, even a CPAP machine (all multi-voltage) I have used simple plug adapters on numerous trips to the UK and continental Europe with no issues, as have millions of other travelers.
There are sometimes issues with hair appliances, and I choose not to bring them.
On a recent trip to The Netherlands, we just used plug adapters, nothing was damaged and everything worked. I wasn't even aware of an Hz difference (or what that means).
Hz is Hertz or the frequency a signal or current oscillates at. AC electric current will either be 50 Hz (Europe and most of the rest of the world) or 60 Hz (North America and a few outlying territories). This is why when you use a North American hair dryer through a voltage converter in Europe, for example, the fan blows slower.