Cant help you on correct tyre pressures mate, but have a look on the sticker on the drivers door jamb sometimes it's listed there. But as a guestimate 55 p.s.i. wont be too far off the mark
The only real answer is to get the front and rear axle weights at your local weighbridge then phone the tyre manufacturer. The Tech department will give you the correct pressures. Obviously the vehicle should be as fully loaded as possible when weighed ie. water/fuel etc
The "stickers" on the doors stating tyre pressures are worse than useless - I can only imagine that they give the value for the maximum possible load.
My old Orian Pavo, based on the Peugeot Boxer, gave pressures of around 60 psi. When I requested details from the tyre manufacturers I was given a list of tyre pressure for a range of axle loads and at full allowable axle load the maximum pressure was 54 psi. With the van partially loaded the rear tyre pressure was only 46 psi.
At 60 psi the van rode as if on solid wheels and gave a very jittery ride. At the correct tyre pressures it rode much better though nowhere near as good as my current an based on the Renault Master.
Get the van weighed for "normal" run-about use, for weekend/short holiday use and when fully laden for a long haul holiday and then you will be able to set the correct tyre pressures for each journey.
There is no such thing as a single "correct type pressure" for the van.