How to get to world 7 in Super Mario Bros for the wii?

I've looked everywhere online for this, but I couldn't find it. We played world 6 and a cannon sent us straight to world 8. We tried going back and finding a way to 7, but we don't know how. Help anyone?|||Dont use the cannon. You have to go to the final castle in world six and then fight on the airship. When you play 6-8 there's an area with fire bros and stuff dont go on the top stay on the boat and keep going to the right. that should lead you to the castle then the airship.|||i love this game can't remember but youtube has it i put it there