weigh the rig, set the tv tires pressures accordingly.
without the scale info no1 can provide appropriate inflation numbers.
this is covered ad infinitum here.....
some might suggest ad nauseum.
with NO brand/model tire listed in the op there's not much point in linking the inflation tables...
besides they've been linked already many times.
IF these are E rated tires on the van they can accept a WIDE RANGE of pressures based on load...
and many folks fiddle with the tables and inflation.
however there's plenty of evidence that running these tires SOFT...
is a NEGATIVE for handling/braking/control and generates MORE tire heat which is also bad.
but for those buying into the "let's make the stream ride sloppy and wallowing"
that evidence is usually ignored.
IF there is no need for E rated tires on the van
go to something else with adequate load/capacity but without EXCESS capacity.
a D rated LT tire can be more optimally inflated IF/AFTER weighing the rig.
or get some nice whitesidewall touring tires, like KINGS/crowns or these...
Radial Tires- Wide White Walls- www.WhiteWallTires.com
it's 3/4 ton van so E rated tires fit the vehicle profile but perhaps NOT your needs.