Outline curve from a solid

Hi Everybody,
I am trying to transfer floors from Rhino to Revit. For this I need the outline curves of the floors. The floors in Rhino are modeled as solids. I don’t know how I can get the outline curve from a solid.
I need the outline curve of the top of the solid.
I hope somebody can help me. Thanks in advance.

In Rhino you can use the DupBorder command on a surface (sub-select from the solid with Shift+pick)

in Grasshopper you can deconstruct a brep and get the surface via list item that you can cast to a curve component.

Thank you for your answer.
I am new to Rhino and Grasshopper. Can you explain what nodes I need in Grasshopper to do this?

No problem, Deconstruct Brep>List Item>Curve

Thank you very much.