How come my new iPhone is asking me to enter my old passcode?

Hi Briana_A,

Thank you for using the Apple Support Communities! I understand your new iPhone is asking for your previous passcode. I am happy to help.

Since you mention this is a new iPhone, did you recently sign into iCloud with two-factor authentication? If so, that would be the reason why that popped up. This can be a normal part of the approval process for two-factor authentication. It is ok to enter it in to continue.

Best regards.