Hello Stefano,
If there are no coordinates for cameras or markers but you need to change the orientation of the model, you can put just three markers on the plain surface and assign them the coordinates that will define the axis orientation. For example, (1,0,0), (0,1,0) and (0,0,0).
Also the orientation of the coordinate system can be changed using Python scripts (assigning the same orientation to chunk coordinate system as bounding box has). But this option is a little bit more complicated.