Kumar Harish

You cannot convert a 3D polyline into an alignment - it is geometrically impossible. You have converted the 3D polyline into a 3D feature. You can only convert 2D data to a geometrically correct alignment.

Try right clicking the reference file > Merge to Master

Mark - in this case I would use 'Copy' as I would not want all the topo details being merged into the working file.

Is the alignment from CAD a 3D Polyline if so use Plan by 3D element

Copy the ACAD centreline into a 2D model in ORD, and use 'Create Civil Rule Feature' to generate the ORD geometry. (If it is a centreline created by Civil3D, it would probably be better to export to LandXML or ifcAlignment from C3D, and then import…