Updating older content, like blog posts, has many advantages. You want to find the most popular older posts on your site, at least ones that were popular, but may have slipped as the information grew stale. Eliminate ones that are about a specific event that happened or ones that you can't update for other reasons. Concentrate on these posts, since you can't update and optimize every one.
The main advantage of updating older posts is that you have already done most of the work. If you included statistics, update them. Include any changes that may have happened and fix any old links that no longer work. See if you can create any new inbound links to other content on your site.
Include new, fresh images or create a graph or infographic to make data more digestible if there is a lot included in the post. There may be places where you could add bullet points or headers to make the content more readable. Making use of H2 and H3 headers can help your SEO.
Fix any grammar and spelling errors. People become better writers over time. If you were not using a grammar checker before, use one now. There are free options for Grammarly and ProWritingAid that can help you eliminate passive sentences and awkward phrasing quickly and easily.
Do your keyword research again. Maybe Google wasn't using Latent Semantic Indexing) Keywords at the time, making your keywords in the post seem forced. Use conceptually related terms this time and see if it helps the updated post gain traction. You may not have to do all these things; just do what you need to do.
Finally, look through comments and remove any that are obvious Spammers often post on old content hoping you will not notice spam. Also, remove any comments that don't relate to the new post. For more information click here https://www.reddit.com/r/SEO/comments/mpy434/doesupdatingoldblogpostsreallyhelpwithseo/.