Returning to Judo after 3 years

Hello everyone, I'm really hoping I can get some advice on an issue I've been having trouble with. I took judo through my college a few years ago and was promoted to blue belt before transferring to a different school. I have recently found a school nearby that I could train at, but I'm not sure how to approach the belt issue. I don't want to be disrespectful toward my previous sensei for promoting me, but I also don't want to be disrespectful to this new school and the sensei by wearing a belt that my skills don't keep with anymore.

Should I explain the situation to the sensei and hope to work back into everything as I remember it, or simply start back at white belt?

Edit: Thank you all for the advice. I will definitely explain my situation to my new sensei next week and get this rust knocked off.