Window Corner

Removing stamped corners like this requires partial disassembly of the frame. The video below will give you a general idea of what's necessary.

We can't identify these while the original corner is still installed. Removal and careful measurement is necessary at minimum. We need detailed, written dimensions and a clear shot of an undamaged corner. 

If you aren't used to this kind of project, it can be very difficult. storms like this are unforgiving and, what's more, they aren't even made anymore. If I were you, I would hire someone to do it for you.