Microphone not detected

I have a problem with my integrated mic on the web cam not being found.

I have done all the things like allowing access through all of the audio settings etc.

Just for clarity, this PC does not have a mic plug anywhere. I used a USB to Mic connector and it doesn't work.

I have a separate mic, and as that has a mic jack I used the USB to Mic connector and that is not found.

I can plug in headphones in the front output jack and the mic works fine. Trouble is I want to use separate speakers so that others can hear the third party. I bought a sound card and that was not recognised by the system. I bought another USB to mic connector (thinking the first one was maybe faulty) and that doesn't work.

I cannot understand why a desktop Pc does not have a mic socket?

Any ideas for a workaround?

Rod