How to export a curve made with MarkupstoModel as STL?

I need to make a model of a nerve which I successfully did using MarkupsToModel in slicer but I need to be able to export this tube as an STL… is this possible? If not I need to find a new way to segment the nerve.

MarkupsToModel output models are surface meshes that you can directly save or export to STL file.