I’ll operate under 2 assumptions here: 1. you’re not a stalker. 2. even if you were, I’m not telling you anything you wouldn’t figure out eventually. I don’t know if you can get any info from the USPS, in fact I would hope that you couldn’t. You could try sending mail and seeing what comes back. Sometimes the new address will appear on the returned mail, but sometimes not. Alternatively, go to one of those websites that find people for money. They actually work, some friends of mine did it (because apparently they lost all the contact info I had given them and therefore had to waste money finding me) and they’re not all that pricey to find just one person.