I’m looking for my old iCloud account

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're talking about passwords stored in a different Apple ID, I do not know of an easy way to transfer them between accounts, only between devices with one account.

"With iCloud Keychain, you can keep your passwords and other secure information updated across your devices."

Read how to 'Set up iCloud Keychain'; click here --> https://support.apple.com/HT204085