If you voted the ballot and returned it, this is identified in the sign-in process at the polls and you WILL NOT be able to cast a vote in person on election day.
The mail-in ballot you received includes a bar code, so if you do not fill out the ballot and decide to vote at the polls, you must bring the ENTIRE MAIL-IN PACKET, which means ALL associated envelopes and papers, to your polling station. Your mail-in ballot can then be properly invalidated and you can vote at the polls.
If you do NOT have the ENTIRE MAIL-IN PACKET when you go to your polling location, you will be asked to complete a Provisional Ballot.