He has 10 charges that were undecided at his last trial. If he gets pardoned the FBI will bring some, or all, of those charges back again and retry him.
In his Washington DC case he pleaded guilty to two counts: conspiracy against the United States and conspiracy to obstruct justice and pleaded guilty to the 10 undecided counts in this Virginia case, so retrying him will be a slam dunk. He hasn't been sentenced yet for the Washington DC case so they're going to be more years added to his prison time
If he's pardoned New York is ready to hit him with a state case that Trump cannot pardon.
How long do you think Manafort will get today?