A picture of the plug on the unit would be incredibly helpful.
As a wild ass guess, I suspect you need a c15 plug. That's the one with the notch. And a 5-15 (standard US wall outlet).
https://www.amazon.com/SF-Cable-NEMA-5-15P-125V/dp/B009Z2GEZY
A list of plug types: https://en.wikipedia.org/wiki/IEC_60320