If you search for specifications for the board, what audio chipset (audio codec) is it supposed to have?
Also: you can USUALLY find out specific device IDs for products in Device Manager, which will help you search.
In this case, double-click on the unidentified PCI Simple Communication Device. Click on the Details tab. In the Property box, select "Device IDs". Right click on the top value & select "Copy". Paste into Google.
Or, to make the search cleaner, take the following as an example:
clean it up into VEN_8086 DEV_9C03.
Often, the results give you an IDEA of what the device is. (For that particular device, it's the SATA controller in my system, and the first result is a site offering a driver download). Then you take that knowledge and search for the proper driver on the manufacturer's website.
(Often enough, for motherboards with actual support -- wherein the manufacturer posts drivers for all the components on a board -- you can just download all the drivers and try installing one by one.)