Hi there,
You'll need a daily recurrence for this.
Your first action will be "Get Rows from a Table". Point the fields to your file, and the table within your file. Be sure to set Date / Time to ISO 8601 in the dropdown. In the filter query, make it ExpiryDate eq 'xxxxx', where "ExpiryDate" is the name of the column that holds your date, and "xxxxx" is an expression which is as follows: addDays(utcNow(),-30,'yyyy-MM-dd')
Then, "Send an Email" - and point the "To" at whatever column you hold that data in. It'll turn into an Apply to Each (but if there's only one entry for that date found, it will only send one; if there's multiple, it'll send multiple; if there's none, it'll send nothing.)
