Unless things have changed, you will report to Clark Hall, where you do most of, if not all of your inprocessing (except CIF). So report in there first and take direction from the staff as to what to do next.

Clark Hall:
https://home.army.mil/drum/index.php/about/Garrison/directorate-human-resources/MPD/personnel-services-branch/fort-drum-in-processing-reception

You could also try to reach out to the battalion you’re reporting to and ask for guidance. Like SSG Unger said though, reporting to Clark Hall is where you will start regardless. I went straight there as well and they processed me into post then contacted my squadron that I reported into and I met my sponsor at squadron and went from there. Enjoy your time at Drum!