how do I get newer articles to use a different permalink structure

I recently switched from a customer CMS to wordpress. My old CMS made urls like this

https://www.domain.com/article/12345

I was able to duplicate this in WP. However, I want to make use of WP slugs for newer and even older articles, but still maintain the old link structure for old articles so that I am not hit with a huge traffic drop in google. Any ideas? Thanks