How to scale my blog?

To scale my blogs, I’m working with a few writers who write good content on a consistent basis. Now, I’m thinking about hiring an SEO virtual assistant who will publish the content on my blog with good On-Page SEO. But, what about the content that was posted 2 years ago which is very poorly optimized and written, but still get some traffic. How I can efficiently improve my old content? I can do that myself but it’ll take a lot of time because there are at least 80 to 100 blog posts. So, if you were in my place, what would you do? Would you hire an SEO to do that? Or Hire another SEO VA who works on your instructions? Or anything else.