Exactly what USB device or “cable” do you have? …A regular USB soundcard might “work” but they are like laptops with only mic-in and headphone-out. You need line-in for a line-level or headphone-level signal.
Plug-in the USB device before starting Audacity or it won’t see it.
Right-click the Windows Speaker/Volume icon and select open sound settings. Then check what Input (or Recording) Devices you have. If Windows doesn’t see it, Audacity won’t see it either.
I only have on cassette
That’s an audio cassette, right? Not a data cassette? You can hear the music with headphones?
male mini plug from tape player to standard USB connector into tne PC.
There is no “standard” USB audio interface… The [u]Behringer UCA202[/u] is popular. (It has RCA connectors) or there are lots of higher-end [u]USB audio interfaces[/u] with switchable mic/line inputs. (These typically have combo XLR/1/4-inch connectors).