Managing Redirect from WordPress-Host to Domain Host, Different Permalinks

Hi everyone,
About six months ago, I migrated a wordpress-hosted blog to its own domain. It all went smoothly and I’ve been blogging at the new domain. But the old blog still gets its own traffic, and I’d like to redirect visitors to corresponding posts at the new domain.

The problem is:
a) don’t know how to set up the redirect
b) there are a year’s worth of posts to redirect
c) the permalinks structure is different

old structure uses dates:
https://rsitreatment.wordpress.com/2008/05/30/what-starbucks-gets-right-its-comfort-not-coffee/

new structure does not:
https://www.rsihealer.com/what-starbucks-gets-right-its-comfort-not-coffee/

Now, I’m happy to change the new structure to match if necessary, but I don’t want to have to do it manually and I don’t want to leave any broken links or ruin any standing I’ve built with google rankings.

Could anyone guide me in how to do a redirect under these constraints?

Thanks!
amy