I'm using a Dell Inspiron 3180 with one headphone Jack available. This means I have to only plug in one Jack. I plugged in my Headphones which only have one Jack and hearing is perfectly fine
However, I can only talk through my laptop mic and the option for my headset mic is nowhere to be found regardless of seeing disabled mics or not. How do I switch to my headset mic?
It is possible that the port you are connecting to either is only for headphones (output only) or it is a cheap version (which happens a lot) and doesn't quite connect correctly with a headset (dual input/output). Additionally, it could be the headset itself that is the problem.
Start with first trying the headset on another device and see if the mic works fine. If it doesn't, then you know it is the headset and not the computer that is the problem.
Now if it works fine on another device, you can try the following, yes I know you said you tried looking for disabled devices, but if you didn't try all these steps I would do so.
If your microphone isn't working, try the following...
Go to "Control Panel".
Click on "Sound".
Click the "Recording" tab.
Click on the device you are trying to fix.
Now click the "Configure" button and then click "Set up Microphone".
Once that is complete, click the "Properties" button.
When you are done with your changes, in "Properties", click "Apply" and then "OK".
Then click "OK", again, on the main "Sound window".
Should this not resolve it, then you have basically three options.
Get the 3.5mm port replaced and see if this resolves it.
Get a different headset that connects via USB rather than 3.5mm.
Get a 3.5mm to USB adapter and connect your current headset through a USB port.