Converting a soldering station from 110 V to 220 V
First check the specs of the unit using its manual. Many devices (such as phone chargers) accept a large range of voltages so that they may be used all over the world, this station may be the same. 

Alternatively, you could find a step down converter that will convert the 220 VAC to 110/120 VAC (something like this: https://www.amazon.ca/Voltage-Converter-220-240-110/dp/B001ES8YY6). Just want to note that simply using an adapter would not be enough because the source voltage would still be 220 VAC.