That is the Side Sill Garnish. Depending on the color of the car which looks like blue the part number should be 71800-SDN-A11ZA for Right Side, 71850-SDN-A11ZA for Left Side. These bolt on with 3 bolts which should still be there, if not someone stole your garnish. They are pricey!!! $375 on up from the dealer. Might want to scrounge salvage yards.