The unit= in most of the m&w stickers creates a category, so it must be named properly. If you do use it, search within the war/country streams and see if it exists (I can tell you that nearly all of the units of US Civil War already exist!). If so, you just lop off the part of the category name up TO the final comma and War and stick it in the unit= parameter. No need to add the category separately at the top. FOREX: if the unit served in was 1st Pennsylvania Infantry during the Civil War, the correct category is 1st Regiment, Pennsylvania Infantry, United States Civil War. SO, in the unit parameter, it would be unit=1st Regiment, Pennsylvania Infantry.
For WWI and II, same thing. Unit=category name minus the final war part.
If you do NOT know the unit, you can leave unit= as blank and fill in the proper branch, and the profile will be placed into the highest level category for the country/branch, like you did with Mr. Hildreth, who is included in United States Navy, World War II.
Units= is free text and won't create a category, so you can tell the story there if you have more than one unit the person served in.