Tube primitive? Or like bbob suggested, delete the end caps and shell it. Seriously if you need help with that, you need to spend some more time working with the software, checking the Help Doc that comes with it and doing basic tutorials that come packaged with the software. If you want a step by step tutorial on how to…
Inset the faces on the cap on both ends, delete the caps, bridge to the center. Add in control loops if you're going to turbosmooth. Alternatively you could try to delete the caps and apply a skin modifer. Been a while since I've used Max, but that may work. Why can't you just create a tube primitive again? To be frank,…