Hello Nataliatran,
You appear to be asking about how to recover a forgotten Apple ID and password which you may need in getting system upgrades for your computer. Click on this link to read what to do "If you forgot your Apple ID" --> https://support.apple.com/HT201354
Click on this link to read what to do "If you forgot your Apple ID password" --> https://support.apple.com/HT201487
or go directly to this link --> http://iforgot.apple.com/
Also read about "What to do after [or before] you change your Apple ID email address or password" - https://support.apple.com/HT204071
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."
https://support.apple.com/HT204169