If you're not familiar with RV power cords, it's important to note that this a 30 amp RV cord, not a 30 amp "generator" cord. The difference is that you need both ends to have the style of connection used in campsites and on the trailer's cord. It is officially known as a
NEMA TT-30 plug and receptacle, but any store selling RV cords will have the right thing. Since they are common, you can wait until you have your trailer and go to a store then (even Walmart has them) when you've seen the end of your trailer's cord so you will recognize the right style.
If you are getting the optional Removable Power Cord, the regular 30-amp RV extension cord will still work, but you have an additional option: you can get a 30 amp cord with twist-lock connectors to go between the trailer and
the removable cord that comes with the trailer. This would be a "generator" extension cord with NEMA L5-30 connectors on each end (a plug and a receptacle). You could wait until you have the trailer and have tried connecting and disconnecting the removable cord to decide which way you would prefer.