Heil makes adapter cables to connect Yaesu modular plugs to XLR microphones. I'm using one on my FT-817 to connect to a Heil hand mic. I also have one to connect a desk mic to my Icon 706MkIIG. A call to a ham radio distributor will advise you as to which adapter and which mic would be suitable. There will be differences depending on whether the radio was designed for a dynamic mic or an electret mic. (Icom). I have an FTM-400 but have never needed a desktop mic as it mainly functions as a node station for Wires-X.