My washing machine overflowed and water ran into my floor vents how to do I get the water out of the vents?

Vents, plural?

Take off the flexible conduit in the cellar, where it connects with the rectangular steel main. You will need wire cutters for the coiled wire, and a knife or scissors for the mylar. Feel around in the main to see if water got in there too. You may have to take the cover(s) off your furnace to look for signs of water. If you see any, call a technician.

Then you will need to reattach the conduit, and that means silver heat resistant tape.

If the conduit sags anywhere before the main, just poke a tiny hole in it and let the water out and let it dry enough to tape well.

I'm speaking as a DIY homeowner.

Supply or return vent? Gallons? Little bit? If a lot of water, go into the basement, find the lowest point on the supply or return ductwork, open the duct up and look for water. If just a little bit, turn on the heater and run it for a while, the water will evaporate.