If your network adapter plugs into your computer, the part number, is on the barcode label. This is a six-digit number, followed by a hyphen, and three more digits. The three-digit number following the hyphen is a minor revision number, and is not needed to identify your adapter.
Using this barcode example, the part number is 721383-006.
Get drivers, and to find PBA numbers, product codes, and PCI device ID information for retail Intel® Ethernet Adapters.Retail Intel® Ethernet Adapter PCI device ID and part number list