If your old account still links to accounts you have access to or if you have other "unconventional" ways to prove your identity, you can send a PM to Tom Fulp, the creator of Newgrounds and figure something out:
https://tomfulp.newgrounds.com/
If you didn't have the pleasure before: He is really kind and approachable.
Tangerine
Welcome back! It's always nice to have a fresh start :)