Hw to fix my account that they are banned on my new iPhone

You talk to Instagram about it, this has nothing to do with Apple.

Here is a link to their help page.

https://help.instagram.com/

It is up to Instagram if they want to allow you to use their service or not. Nothing Apple can do about that. A ban can be a temporary ban or a permanent ban and it makes no difference on what device you use.

Exactly where did you get the phone? Sounds like you bought a used phone that had already been banned by instagram. Probably why the original owner sold it.