
Hey @Audi86 some good news here I think. Microsoft triggers this automagically, you shouldn't have to do anything. Manager (if specified) receives link and notification at 30 days, with a reminder at 7 days.
You can also change the period beyond 30 days if desired, and once deleted the OneDrive will be in the recycle bin. Take a look at this article.
https://learn.microsoft.com/en-us/onedrive/retention-and-deletion