My van makes a squealing sound

You have 2 Serpentine belts on the left side (looking from the front) of your vehicle, these wear over time and become stretched and loose, replace BOTH as it could be either of them and when one is worn,,, the other will not be far behind. Belts are not expensive the top is pretty easy to do, the bottom which drives the power steering pump you have to remove a plastic panel in the front left(looking at the vehicle) wheel well. good luck:)

Its one of the belts on your motor. Did you drive through a huge water puddle in the last few days? It sounds like they are wet.