Hello. You have selected the correct one. Microphone Array is the internal mic. It is a pair of mics located in the webcam assembly at the top of the display screen.
The things you can try are
> Reinstall the IDT audio driver from the Inspiron 14z 5423 support page. When you get to that page, first select your operating system by clicking on the Change OS selector:
> Adjust the mic volume and boost. Here is a screen shot of the path, but on yours start from Microphone Array:
> If you have a program in your list of programs named Dell Webcam Central, open that program and find the microphone settings. Make sure the mic is not turned off.
If none of those things fix the mic, it could be damaged. To fix the mic array would require replacing the webcam.