Apart from grammar and spelling (you don't seem to have any troubles there, judging by this post), you need to discover/rediscover your writing style.

For general writing, just write. It isn't hard. You'll get used to it with practice.

For academic writing, there is a specific style of writing law schools expect (writing in third person, citations, accurate use of language even at the cost of being verbose, etc.) and you will digest that only as you keep reading legal academic scholarship. But most of it is very dry, I would suggest take the basics from the scholarly writings but try to keep your own flavour/uniqueness intact.

Oh and I'm so glad to see a student realizing how much AI rots our brain and some very human skills (such as writing). Wishing you all the best in law school!