Hi xoharrz,
I'm Rodrigo and I will help you.
The mic plugged in the TRSS connector on your laptop will show in the same input device of your laptop's integrated mic (not Stereo Mix), but to work, you should set the plugged device as headset on Realtek control panel.
You can find the Realtek control panel on the taskbar, next to the volume icon, if you do not find it there, open the start menu, type control panel and press Enter, set "View by" to "Large Icons" and find the the "Realtek Control Panel" or "HD audio panel" or something similar, with the headset plugged in, double click the connector icon and select the connected device as "Headset"