Depending on what model, anywhere from about a 3.2 tonne train weight and 5.6 tonne train weight (train weight includes it's own weight as well as what is behind it.).

The question is to general to be specific without seeing the chassis plate it's difficult to say. Once you know it's train weight then you need to know how much the van weighs to subtract the lower figure from the higher figure to give you the allowable weight you can tow.