There's no reverse switch. The hose is in the blower port and should be in the port on the red drum of the vacuum.
I might be wrong, but that looks like it was made by Shop Vac. I believe they make the wet/dry vacuums for Dayton as well.
Used Wet/Dry vacs are a dime a dozen. I would recommend a Ridgid at your local Home Depot. You don't know how much life is left on the motor since it was used in a concrete application. That dust is the Achilles heel to bearings.