Problem transferring apps from IPhone 7 to IPhone 13

[SuzK]

Bought a new Apple iPhone 13  after owning an IPhone 7. Updated both the old and new phone to IOS 15. Backed up the IPhone 7 both on ITunes and ICloud. Started the transfer from old to new phone with the "side-by-side" method, and all seemed to go well, until the "finishing up" step. At that point, the old phone showed something like "completing transfer of apps" and that's when it hung up (the spinning "circle" thingy). Left both phones plugged in and on overnight, but no progress was made (so the old phone has not yet been erased). Next day the IPhone 13 shows all the IPhone 7's app icons but many don't work (calls do work, however). Here's my real problem: In the IPhone 13's settings, it said "complete the transfer", and asked for the IPhone 7's passcode with only 4 digits. BUT, but, but, the IPhone 7 has a 6 digit passcode.  Now what do I do? Thanks in advance for your suggestions.