Burlmart,
You might find when you go to a big store like HD there may be choices galore. The 30 Amp 120 volt plug in you need is just that, but there are a great many three and four prong plugs and receptacles all for different uses. The 50 amp ones the big DP's use is a different plug, and there are many more, each for a unique application.
It is vitally important to connect the wires correctly if you replace something electrically. If you can see the connections from your present plug in cable, and the color of each wire and where it goes in your panel, you will need to know which terminal each goes under if you replace the cord cap (plug).