Follow these steps to locate or create your D-U-N-S number.
First Sign into your iTunes account here, if you don't have one, create one here.
You may already have a DUNS, click here to search for it.
After entering all your information, click submit, if you already have a D-U-N-S number it will email it to you. If you don't have one, the page will prompt you, asking if you'd like to forward your information to D-U-N-S, click yes. **NOTE** Please make sure the address associated with your D-U-N-S number is accurate. If it is not up to date, Apple may require that an update be made before we can move forward.
This will take about 5 business days to get a D-U-N-S number back. Once you receive your D-U-N-S number, you may be required to wait 7 days before using it. If so, you will be required to wait 7 days before you are able to enroll in the Apple Developer program.