How do I find the father of my child.

Briefly, I was 20 when I became pregnant, and my baby was born nine months later. Nine months after that, my boyfriend left us. He would visit occasionally, but those visits dwindled, and it’s been about six years since he last saw us. My son is 10 now. I recently lost the biological dad’s phone number when I changed phones, which worried me because I still wanted a point of contact even if he never used it. He still has our home address and my email,(I lost his email address when wiping my emails) so he could reach out. My son has asked to meet him recently and I have tried everything I can to track him down. Does anyone know how to track a person down?

Thank you