Where do I find the passcode for my iphone

See If you forgot the passcode for your iPhone, or your iPhone is disabled https://support.apple.com/en-us/HT204306

The instructions are essentially the same for an iPad and iPod touches. “If you enter the wrong passcode too many times, you’ll see a message that your device is disabled. If you can’t remember your passcode, you'll need to erase your iPhone, which deletes your data and settings, including the passcode.”

If you backed up your iPhone, you can restore your data and settings after restoring your iPhone. If you never backed up your iPhone before you forgot your passcode, you won't be able to save the data on your iPhone. Follow the steps below to remove your passcode.”

Next, remove your passcode (see the document for the steps). Then, restore you phone of your computer (see the document for the steps).

“If you can't update or restore your iPhone using recovery mode, or you can't use recovery mode because of broken or stuck buttons, contact Apple Support. Then follow the steps to set up service for your iPhone.”

The pass code must have been set up by YOU. There is no way of finding this if you have forgot.

You can try to restore your phone here. If you've forgotten the passcode on your iPhone, or your iPhone is disabled – Apple Support

Bear in mind that if you have any backups you will not be able to access them as it is encrypted data and it also requires the pass code.