You cannot change the incoming power on a unit as easy as changing the cord. If the unit is wired for 208/240 a cord isn’t your fix. The ultimate fix is wiring the unit for the appropriate voltage. Your unit is meant to run on whatever voltage is labeled on the data plate. Please review the data on the data plate and ensure it is plugged into the correct voltage.
Techjoeb is correct, but there’s still more to it. To configure the steam table to another voltage, all of the heating elements would need replaced with ones rated for that voltage. Additionally, if it uses infinite control switches for each well (vice thermostats), then all of those switches would need replaced too.
Your best and most prudent choice is to hire a licensed electrician to add an outlet which supplies the proper power to the steam table.