Moving parts of the body of an object created with Daz study

[iacoposk8]

Hello to all! when I create a template with Daz Studio and then export to obj if I try to import it into Blender I have problems.

The model is seen correctly, but I do not treat it as a single object, I can only select only the thigh or forearm, etc. .. just that if I try to move them I break off from the rest of the body.

how do I raise / lower the arm holding it attached to the rest of the body? thanks