Perhaps the reason you've had no replies is that people think you should be
able to figure this out yourself.  I've never seen an evaporator drain that
wasn't coming directly out of the bottom of the evaporator housing.  Locate
the housing and you've located the drain...

If your problem is that you can't figure out where to find the housing, try
following the refrigeration lines to the firewall.  The box they go into
will house the evaporator.  If that doesn't work, then just crawl under the
van and look under the passenger floor near the firewall.  This isn't rocket
science, it's just going to require you to put forth effort to look.

CJB

Nope.  But it's gonna be somewhere under the car.  I found the one on
my son's crown vic this summer and cleaned out some gunk.

Just start under the passenger side of the vehicle, checking along the
firewall.  Often there is a hose that leads down to the floorpan.