how long does it take to transfer data from old phone to new phone?

Refer to this document for the different ways available --> Transfer data from your previous iOS or iPadOS device to your new iPhone or iPad - Apple Support

The amount of time it takes will depend upon the connection method (wired is usually faster) and how much data you have. It could take hours if it is a slow connection, or it could take 10 minutes if there's not much data and the connection is fast.

A while.

Of course, we know absolutely nothing about the method of transfer you might be using, or anything about your particular scenario.