Ho do I convert an "EagleCAD 5.12" project to "KiCad 5.0.2"?
The KiCad Eagle importer is based off of the Eagle 7 DTD but should also work with Eagle 6 files.  Your file may need to be converted before it can be imported.  You could try this using the Eagle 7 program (Open in Eagle, re-save then import)