How can I fix my mesh in RC so I can sculpt the mesh in Blender without the texture breaking?

Thank you for the response.  I am trying this now.  I’ve smoothed out some parts and recreated the back part of the pillow so there is no hole.  But once I import the model (MESH MODEL>Import>Import Model), the model fails to load and I get the error attached error messages.

How do I fix this so I can import my model and retexture it?