Here are the three types of adapters that most people carry.
The top one is a 15 amp male to 30 amp female dogbone. The big end attaches to the outlet on the side of your T and the little end you plug into a contractor’s sized (15 amp at least) extension cord that you plug into your house outlet.
The middle one is a 50 amp to 30 amp dogbone that you use at a campground that doesn’t have a 30 amp outlet available for you to plug the OEM shore cord into. Most people rarely need this one.
The bottom one you can put on the shore end of your OEM shore cord that allows you to plug it into your house outlet.