Thank you and BLESS you Tremi the article was exactly what I needed.
Just in case anyone else decides to go this route here is what I did, mostly per the article:
Downloaded the WordPress plugin Simple 301 Redirects and activated it.
Just in case, I deactivated the other plugin.
I copied each soon to be changed url from my blog,
pasted it into the Request and Destination areas,
then removed the https://www.avivopur.com part and
removed the date from the Destination area.
Save and repeat for all remaining blogs I wanted to update. (Whew!)
FINALLY I went to settings/permalinks and changed it to just post name and all blogs instantly changed BUT all exisiting links I checked “out there” still work and redirect. As a bonus I renamed my /hello-world/ blog to something more meaningful too. ??
THANKS AGAIN!!!!!
