A common standard for Yaesu radios is the 6 pin mini DIN plug. The easiest way to get a wired 6 pin mini DIN plug is to buy a plug-to-plug cable, commonly available on eBay, for around £5-6, and cut it in half. Then you have two!

All you need to do then is work out (with a multimeter) which pin corresponds to each wire, and tack them to the pins on a 9 pin D shell plug as follows:

Pick pin 4 if you'll be using 9600 baud, or pin 5 if you're using 1200 baud. You might be able to use pin 4 for 1200 baud as well.