Unless you stored them on a backup drive, your only way to get access to them is to sign into the old account. You do not provide the reason why you lost access to the account so it is hard to tell where to start.
This document tells you the various ways you can try to discover your forgotten Apple ID --> If you forgot your Apple ID email address or phone number - Apple Support Note that typically this is an email address you use.
This document outlines what to do If you forgot your Apple ID password --> If you forgot your Apple ID password - Apple Support
or go directly to this link --> http://iforgot.apple.com/
If you find you can’t sign in, reset your password, or receive verification codes, you can request account recovery (read this support article: How to use account recovery when you can’t reset your Apple ID password - Apple Support ) to regain access to your account. Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity.
If you still need help:
Contact Apple for help with Apple ID account security "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues." Click here --> Contact Apple for help with Apple ID account security - Apple Support
