There's no trigger for nothing happened, so you could run a scheduled flow that runs every day, and it lists rows on the required table with a filter of modifiedon > 3 days and < 4 days which will produce a list of those last modified 3 days ago.
Filter would be something like
modifiedon gt var3DaysAgo and lt var4DaysAgo
where the var4DaysAgo would be like:
concat(formatDateTime(adddays(utcNow(),mul(variables('Days'),-4)), 'yyyy-MM-dd'),'T00:00:00Z').
Hope that makes a modicum of sense !