I'm sorry you lost your uncle. Right, there is only the 785th, so you'll have to create the category. Luckily, the Military and War Project has such a great organization of categories so it should be easy.
This is some code for a World War II sticker. It will show an American Flag:
{{World War II|United States Marine Corps||28th Marine Regiment;1st Marine Division|unit=1st Marine Division}}
You'll just have to change the information to your uncle's.