Unable to enter 6-digit code during iPhone erase process

If I press erase iPhone it asks for all my passwords and then it needs a confirmation to get into my iCloud from my other phone. If I press allow it gives me a 6 digit code but nowhere to enter it. If I press don’t allow, nothing happens. How do I wipe my phone?

[Re-Titled by Moderator]

Original Title: Erasing iPhone