I forgot my iPhone passcode

You can't.

If you forgot the passcode on your iPhone, or your iPhone is disabled -

How to reset your passcode without a computer if you have iOS 15.2 or higher.

How to reset your iPhone, iPad, or iPod touch when you forgot your passcode - Apple Support

How to reset your passcode using a computer.

If you forgot your iPhone passcode - Apple Support

Have you forgotten your passcode?, 

(< iOS 15.2) See this Apple article: If you forgot your iPhone passcode

If you forgot your iPhone passcode - Apple Support

(iOS 15.2 and newer) How to reset your iPhone, iPad or iPod touch if you've forgotten your passcode

How to reset your iPhone, iPad or iPod touch if you've forgotten your passcode – Apple Support (UK)

Have you forgotten your password? -> See this Apple article: If you forgot your Apple ID password

https://support.apple.com/en-us/HT201487

Then see this Apple article: What to do after you change your Apple ID or password

https://support.apple.com/en-us/HT204071