Create Automation Notification on Inactive Items

I’m trying to create an automated notification to ping the Item owners within a board when an Item hasn’t been updated in 30 days. We are trying to get better data quality in our boards so i was thinking - to do this I added Last Update Date column to the board and then I created a formula field (ADD_DAYS({Last Updated#Date},30))

However, i can’t select this formula field in the automation builder. So i’m wondering if others have created similar notifications and have a work around.