3.5 mic input to lg jm45 shelf system

[mastrc01]

What type of adapter can be used to use a miccrophone with soundbar output for karaoke system. It has only usb input. Want to use for vocals with 3.5 mm miv

 

[Alabalcho]

A lot of things you mention needs additional clarification:
- What is this "microphone with soundbar output for karaoke system"? This sentence containg three separate devices - microphone, soundbar, and karaoke. Which one is which?
- Karaoke systems usually have their own microphone input.

I can't find anything about your "lg jm45 shelf system", but if it has "usb input" only, this USB input is for USB Memory Key only, so that your "shelf system" can play MP3 songs off the key. You cannot use that USB input for anything else.