How to delete Sent Items on an Exchange Mailbox

Hi All

We have an Exchange Online shared mailbox where we want to automatically delete anything in the Sent Items folder more than a week old.

None of the old ways of doing it work anymore, so I'm guessing I'd have to use MS Graph, but I'm absolutely lost on how to set that up. If you can point me at an idiots guide for doing it, I'd be very grateful.