What to do about old articles?

Hello SEO people,

I have 300 to 400 articles that are old and are not SEO optimized. Most of them have around 500 words and, even though I wrote them, the style of writing is different from the present one.

The articles are not published but are part of a backup. What should I do about this? Should I try to use the old articles in any way?

I'm thinking that Google wants articles to be longer than 1000 words and writing an additional 500 words to a few hundred articles is going to be painful. Even more, considering the writing style is different in the old articles, I should rewrite them all.

On the other hand, the simple way would be to just publish them as they are and hope for the best.

Will Google penalize me if I have too many articles that are not optimized for SEO?