What part is this?

try an on line parts place, they should have break out drawings. maybe camelback toyota or the like

 

I usually call the Toyota dealership parts department to identify parts that are confusing to find. But it’s better to go to the dealership parts department in person since it’s easier to pin point it on their computer without guessing over the phone. That’s what I did the last time I needed a part that was hard to identify. It is an exhaust heat shield, hopefully you find the right part for it.

 

Is it just one of the fastener holes tore out? Maybe an oversized washer (get galvanized if possible) would work. They're often referred to as "Fender Washers". They're readily available at hardware stores.

Washers Selection Guide | Engineering360

 

I have the 2010 too and the same heat shield is broken exactly like yours. I also couldn't find the Toyota Part Number from their part diagrams.
Did you fix yours? Do you have the P/N? How much did it cost you?

 

That one looks like the Fuel Tank Shield. Part Number 7764147020. Found it on the diagrams under FUEL TANK & TUBE:
FUEL TANK & TUBE. 2010 Toyota Prius | Toyota


The other heatshields are here and it has a reference where to find the Fuel Tank Shield one:
FLOOR INSULATOR. 2010 Toyota Prius | Toyota


Make sure to confirm the part number with your exact VIN. At least now you have where the look in the online parts catalog.

 

That one looks like the Fuel Tank Shield. Part Number 7764147020. Found it on the diagrams under FUEL TANK & TUBE:
FUEL TANK & TUBE. 2010 Toyota Prius | Toyota


The other heatshields are here and it has a reference where to find the Fuel Tank Shield one:
FLOOR INSULATOR. 2010 Toyota Prius | Toyota


Make sure to confirm the part number with your exact VIN. At least now you have where the look in the online parts catalog.