I have a JBL T380A headphone, and it broke near 3.5mm jack. Do I have to replace this 3.5mm jack or can I combine these wires with an existing 3.5mm jack?
It’s possible to fit a new 3.5mm plug, but that particular type of cable (looks like polymer core and enamelled copper) is very difficult to solder satisfactorily. A replacement connector will seldom be as durable as the original moulded-on part. If you know somebody with adequate soldering skills (I’m guessing this isn’t you) then they may also be able to identify the pin out - show them the old connector.