You probably need to create a WinPE image which integrates drivers for your network card.
This tutorial shows you how to do this : DISM Tool – WinPE 3.1 Boot Environment. Step 5 is where the magic happens.
As for the drivers themselves, you can get them from the excellent DriverPacks website. By adding the content of the DriverPacks LAN package, your new WinPE image should have no trouble recognizing your network card.