WPDB Insert or if exists Update

I’m not crazy familiar with WPDB or SQL in general but I have a custom table for my project and I’m trying to assign some metadata to it. What I’d “like” to happen is if a row exists, update it and if not insert it. I’ve read both Insert and Update in the WPDB Codex but neither really went into an “either or” situation. I thought i could work with update, so my code so far looks like this: