To run the newer versions of MacOS this system supports you’ll need to upgrade the systems firmware as outlined
Sorry I don’t that much on the cheese grater Mac Pro for part options. We only used Apple parts where I was working at the time. We had a business account with Apple allowing us access to Apple spares. This is the better Apple unit [https://www.thebookyard.com/product.php?cPath=87_207&products_id=11701|Mac Pro SuperDrive (Apple) - 18X, Apple P/N 661-5681]