How can I get my passcode for iPhone 11

You can't get it. You will have to reset it.

If you enter the wrong passcode on your iPhone Lock Screen too many times, an alert lets you know that your iPhone is disabled. (Learn what to do if you see "[Device] unavailable" or "Security Lockout" on your iPhone or iPad.)

Lock Screen Passcode or Screen Time Passcode.

Following this process is the only way out if your iPhone is disabled. The steps given in this link will help you reset the passcode -> If you forgot the passcode for your iPhone, iPad, or iPod touch, or your ...

Note: If you have forgotten the Screen Time Passcode then restoring your device from a backup after the passcode reset will return the Passcode back to your device. So, please do not restore from a backup.

Your iPhone needs to be erased and set up again after that.

In case your iPhone has iOS 15.2 or later installed, follow the steps in this article:

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

For older iOS versions follow this one, to erase it, using your computer:

If you forgot your iPhone passcode - Apple Support