Change drain plug to Fumoto w/nipple or oil drain kit, VP 3.0GS

[meangreenBP]

I did not check the drain plug when I had it out for oil change and now I want to order a fumoto oil drain valve with nipple so I can run a hose out the back of the boat next oil change. So what size?? standard or metric? The Glastron is a 1998 Volco Penta 3.0 GS MBY Serial #4110164927.
Thank you