What is the six numbers of my iPhone passcode

To unlock your iPhone, follow the steps described in the Apple article:

(< iOS 15.2) ->: If you forgot your iPhone passcode

If you forgot your iPhone passcode - Apple Support

(iOS 15.2 or iPadOS 15.2 and newer) If you see an iPhone or iPad unavailable message or Security Lockout screen

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

iPhone 8 Plus, iOS 12

Check iPhone model & iOS version -> Go to: Settings -> General -> About.

If your iPhone is eligible for an update, you can check by reading this Apple article:

iPhone models compatible with iOS 12 -> iOS 16.

iPhone models compatible with iOS 16 – Apple Support (UK)

Go to Settings -> General -> Software Update -> Download and Install.

You need about 6 GB device storage and good Service and/or Wi-Fi.

If they are On, turn Off Hotspot & VPN.

Charge the battery > 70%.

See the following Apple articles:

Update your iPhone, iPad, or iPod touch

Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If your iPhone, iPad or iPod touch won’t update

If your iPhone, iPad, or iPod touch won't update - Apple Support

You can do the update via PC, see this Apple article: Update software on iPhone, iPad or iPod touch in iTunes on PC

Update software on iPhone, iPad or iPod touch in iTunes on PC – Apple Support (UK)

If you have a Mac see this Apple article: Update your iPhone, iPad, or iPod touch with the Finder

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support