How to get serial number

You can read the serial number from your current / previous iPhone on the box you show the picture of.

The serial number starts with "F2L"

You can also find the serial number of your iPhone in the software on your iPhone, see here:

Find the serial number or IMEI on your iPhone, iPad, or iPod touch - Apple Support

If you forgot the code for your Apple ID / iCloud look here:

If you forgot your Apple ID password - Apple Support

If you also forgot your iPhone's password, see here:

If you forgot your iPhone passcode - Apple Support