If you want full size this item or print in parts, you need use other slicer. Not Creality slicer. Use other slicer, maybe prusha slicer. Dowload model, 3mf or stl and upload in slicer. Use function "Split"->"To objects"Print easily in parts.

3D model description
500mm X 260mm

Moved.

Write me if find erros, or there are suggestions for improving the model