How can I recover my iPhone passcode without losing data?

If you forgot your new passcode, you may still be able to get access to your iPhone within the next 72 hours with your old passcode. Otherwise you will have no choice but to erase your iPhone and restore from a backup. Without a backup all your data will be gone.

Temporarily use your old passcode when you forget your new passcode on iPhone or iPad - Apple Support

Meeeeeeetoo wrote:

How do I get into my phone without delete everything? I can’t remember what I reset my passcode to today

As long as your iPhone is updated to iOS 17 or higher, you can use your previous passcode once to get back in by following the directions in this link --> Temporarily use your old passcode when you forget your new passcode on iPhone or iPad - Apple Support

If you don't remember the previous code or your iPhone isn't on or can't support iOS 17, your only other option will be to erase the phone using your computer, then setting it up again from backup (assuming you've been backing up your iPhone). See how to do that here --> If you forgot your iPhone passcode or your iPhone is disabled - Apple Support