Start by having your Raspi turned off/shutdown (perform a clean shutdown!) and then plugging in your USB audio card. Then boot the Pi as normal.
Once you log in, type dmesg | grep cm109 to look at the boot messages. You should either see some lines about cm109 if you have a CM109 chipset
or if nothing comes up, try dmesg | grep C-Media you will see some C-Media notes but no mention of the cm109 driver. This means its a CM108 or PCM2902
or if nothing comes up, try dmesg | grep General you will see mention of GeneralPlus. This means it's a GeneralPlus