Thank you everyone for your help so far.
So to report in person, do all I need are my passport and the TM47 form? Can I grab the form at the immigration office and fill it there?
Additionally, I am planning to go apply for a change of visa to Non-O next week (doing it a bit early as my current extension allows me to stay until Dec 2).
Since I will need to go do the 90-day reporting in person as well, I'm thinking I might as well apply for Non-O on the same day, then do the 90-day reporting. Hopefully, it will not be deemed too early for me to apply for Non-O.