Could not access old iphone due to forgotten password

If you forgot the Apple ID password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification email option if necessary. Link to contact Apple Support at the end of the 2nd article.

Apple ID - Manage            

Apple ID – Forgot Password            

If you need the passcode

Passcode - If you forgot the passcode for your iPhone or your device is disabled.  

Hello juliannaduran89, there is a possible option which is to enter recovery mod eon your phone, you do this by pressing and releasing the volume up button and the volume down button simultaneously, then, hold down the Side button until the Connect to iTunes screen appears. Then a pop-up window will show telling you that your phone is on recovery mode, and it will ask you to restore your phone it may take a while but when your hone loads you can download your iPhone backup from iCloud.

Cheers!