Well there’s your first clue. The pipe command in rhino and grasshopper will create a surface around a centerline curve. It’s up to you to determine where and what shape your curves should be.
You will get much more useful help here if you demonstrate that you have at least tried. it will also help make your questions more specific.
Please see this post, in particular number 7
https://discourse.mcneel.com/t/how-to-ask-effective-questions/50034