I think it's best to purchase the RV 30 amp extension cord and then use the dog-bone adapter from shore power plug to the extension cord. This way, you also have an extension cord you can use when camping. You never know when you may need to use more cord than is available with what "just" comes with your camper, especially when camping at a new campground you've never been to before. You just never know what to expect, this way, you are prepared if you need it. Photo below shows I used (one) of my 50 foot cords, because the 35 foot that's installed in the camper was just too short: