The common corruption practice of past governors was the embezzlement of funds met for infrastructural development.
The suitable punishment is to track where the funds were diverted to. If the money is still in the bank, the account should be frozen and due diligence should be to retrieve it back to the state. If the billions were used for other establishments in the name of the governor, the properties should be confiscated.
The governor should be made to face some years in prison for such corruption acts. If he is a serving governor, he should be impeached and should not be allowed to hold any elective post in the country.