Hello SHARONkay66,
Thanks for using Apple Support Communities! We see you have a question about a passcode request when setting up your new iPhone, and updating your iPad, and we'd like to do what we can to help.
We're not quite sure why that is happening, however, we do have some information we can share, which will hopefully help you out.
When asked to enter the iPhone passcode on the iPad, make sure that you have already used the new iPhone passcode to unlock your new iPhone at least once.
We also want to be certain that you're not being asked to enter in an Apple ID two-step verification code, or two factor authentication code. Here's info about each of these Apple ID security methods:
Two-step verification for Apple ID
Two-factor authentication for Apple ID
Another thought is setting up iCloud Keychain:
Set up iCloud Keychain
We don't want any personal information to be accidentally shared in this forum, so if you need additional assistance, please contact Apple Support. Let them know the exact step you are on, what the verbiage on the request says, and any error message. That will really help.
Get Support
Enjoy your new iPhone 12 Pro Max!