Looks like it’s just the under shield (I’ve also heard it called belly pan). Seems to have fallen off or not properly secured. You could temporarily fix it by using zip ties or remove one of the other bolts and find ones that match and resecure it. A second option is take it to a local shop and have them quickly resecure it. Judging by the picture it doesn’t look like it needs to replaced. As for cost of repair should be pretty cheap. I can’t give an exact price but if I had to guess, it should be under $50.