how to get rid of mildew smell in basement carpet?

Remove all the carpet and pad and discard. Toss-out any fabric covered furniture as well. Place a dehumidifier or 2 in this basement and run them 24/7. Be sure to empty them daily. Be sure to mop the entire area with a 50/50 mix of Pine-Sol to stop any mold from growing back-(20 times more effective than bleach). Mop every three weeks or as neccessary. Do this religiously to stop all mold 'cause moldy basements will mold the rest of your home. Moldy homes will kill you way before your time is up.

How was the water removed? Was it professionally extracted? Consider having the carpet professionally cleaned, this will remove any bacteria and mold that is growing. Bacteria and mold is what you are smelling and you can not properly remove and treat this yourself. If there is padding, it might need to be removed.

Start with a dehumidifier...get the old rugs out, clear out the stuff that's in the basement and allow salvagable items to air out and spray them down with a disinfectant. I would recommend Oust or Febreeze for the smell...

That's a tough smell to get rid off. But the best thing to do is try CINIMMON INCENSE and Vanillia cleanser. They sell the VINILLA CLEANSER in the SPANISH TYPE SHOPS it really helps.

Sprinkle baking soda all over the rug and vacuum it up the next day or so.

Good luck