How would I find the code to apple iPhone 8 Plus

Sorry to hear that. If you did forget the passcode you will need to restore the device. 

I’d follow this article 

https://support.apple.com/en-us/HT204306

When you set it up again try restoring from an iCloud backup. If you have it great if not you will need to set it up as new and get sighted back into your accounts. 

You just might be surprised how much of your stuff you get back