To Convert a Mesh Object to a 3D Solid

At the Command prompt, enter SMOOTHMESHCONVERT and specify one of the following conversion options:
- Smooth, optimized. The resulting model is smoothed, with merged faces (SMOOTHMESHCONVERT = 0).
- Smooth, not optimized. The resulting model is smooth, with the same number of faces as the original mesh object (SMOOTHMESHCONVERT = 1).
- Faceted, optimized. The resulting model is angular, with merged, planar faces (SMOOTHMESHCONVERT = 2).
- Faceted, not optimized. The resulting model is angular, with the same number of faces as the original mesh object (SMOOTHMESHCONVERT = 3).
Click Modeling tab > Solid panel > Convert to Solid.
Select a mesh object that has no gaps or intersecting faces.