Stay Safe and Photograph the Flood Damage
Do not walk into standing water while the power is on. Have the electricity shut off at the meter or main panel, and call the gas company if you smell gas. Wear boots and gloves, because flood water is dirty.
Before you tear anything out, take photos and video of every room, the water line on the walls, and damaged belongings. Contact your insurer early and ask what they need to see. We can't promise how any claim will turn out.