Vin should be two places. First and probably the easiest to find is the vin plate at the left (street) front corner of the trailer. Second will be on the "A" frame somewhere. OR possible on the skirt at the front of the trailer. Probably so much paint on the "A" frame it is not berried. If the vin plate is missing or totally worn out, then it will probably be time to get the wire wheel out and grind off all the paint.
Don and Lorri
2007 Dodge 3500 dually