how much time will my fiance do or wat will happen

It's definitely not a good thing that he picked up the new case; especially since it's essentially the same kind of case (burglary and theft are both basically thefts). But, there's no guarantee he'll do prison time. It really depends on the County in which he is charged. It depends on the facts of the new theft case. How long he's been on the probation. What kind of probation he's currently on (straight probation or deferred). Any prior criminal history. There's a bunch of factors that go into what happens next. If he doesn't already have one, he needs to hire an attorney immediately, to try and minimize the damage.