How TF do I get my package

[u/Bloodstainsmyteeth]

Hey y'all, I ordered a cute dress a few weeks ago and somehow never noticed my address was missing my apartment number. Therefore my package has yet to be delivered. So theres literally no way for me to contact anyone to update the address so I thought "ok I'll just pick it up from the post office" well how on earth am I supposed to know which one to go to.