Something like this:

10A converter:

https://www.amazon.com/Voltage-Regulator-Converter-Waterproof-Transformer/dp/B07V9D6SF2/

20A converter:

https://www.amazon.com/Kohree-Converter-Regulator-Transformer-Waterproof/dp/B09GXXQZ6P

You need to read the maximum current that the motor draws, to see if 10A or 20A (that means 120W or 240V) is sufficient, or you need something bigger. If not sure, go bigger.

Yes, they say 24V input, but IMO they will work for 18V too. Worse case, you return them.

They state: "Wide input voltage from 18V to 35V"