There is no process for a revote. It will go to the state assembly to decide.
If, contrary to a direct order from a sitting Supreme Court Justice, the crapweasels in Philadelphia "mixed" the ballots, the Court could reasonably say "Whatever the count was at 8PM on election night is the final count" and Trump gets all the state's electors.
The Supreme Court CANNOT modify election law, but it can dissuade f*ckery.