If your move to FL was "permanent", then you would be a FL resident even if you were only in the state for a few months (or a few days).
As a FL resident, you would file a part-year resident MI return reporting the income earned while you were a resident of MI. That would also include whatever interest and dividends were paid to you while living in MI.
Your FL income would not be subject to MI state tax, and that would include interest and dividends were paid to you while living in FL. FL has no income tax, so you wouldn't need to file a state return for FL.
