what is military/army writing format regarding essays.?

Get with one of your admin folks and they can tell you about the format to follow. That will include what font and pitch, how much border and line spacing you can use. Yes; the majority of it should also be in first person, active voice. While this might be difficult for you in some ways its a good lesson for you in more ways than one. You can't and won't get promoted in the military past E-4 without having some good communication and writing skills. This also is probably better than him giving you a verbal counseling or LOC which would then delay your next promotion temporarily at least. He just might be looking out for you and your best interests here and it sounds like you have a decent NCO so DO IT and learn from this task and not to be late and the problems it causes when you are!

No such thing as a military format for writing an essay. Not sure how one could write 1000 words in an essay. An essay is just 5 paragraphs.

It's a THOUSAND WORDS. This is punishment, plain and simple; you're not writing poetry or the Great American Novel. Don't worry about formats, it's like high school: Just write the damned thing, talk about why being on time in the Army is important, ramble on if you need to, check your spelling, and don't be a dumbazz about it.

Just make sure you have a thousand words and that you stay on topic.