"So I was wondering how long does the State Attorney have to formally file charges against me?"
Depends on state law. In my state they have 5 years to prosecute general felonies. As long as there isn't a dismissal with prejudice, they can dismiss and refile over and over again.
"the State Attorney has 30 to 45 days to formally charge me from the date of arrest, but if they don't the case will be dropped.... But she also told me that they can pick the case back up again??? I'm confused..."
How is that confusing? The statute of limitations runs from the event, or possibly discover of the theft since thefts are secret by their nature. The statute of limitations on a felony is likely several years.
Dismissal does not stop the state from refiling unless it is a dismissal with prejudice. If they never file something in the first place, there's no dismissal.
You have a constitutional speedy trial right that runs from the arrest. You may have a statutory speedy right that also runs from arrest, and requires an information or indictment within X amount of time.