Found this and it worked great:
https://www.2020hindsight.org/2004/07/07/searching-and-replacing-within-phpmyadmin/
It’s basically this code in PHP MyAdmin, click SQL:
update 01_posts set post_content = REPLACE(post_content, "what I want to replace", "the replacement text");
I use numbers “01” instead of “wp” for my multiple installs, so make sure to change that prefix to the tables in question.