I don't know anything about drip.co, but it looks like the best bet for anything like that would be to create and save a search for members joined a certain amount of time, then use that search, export the results to a CSV file, and use the CSV on drip.co as an import.
I don't know anything about drip.co, but it looks like the best bet for anything like that would be to create and save a search for members joined a certain amount of time, then use that search, export the results to a CSV file, and use the CSV on drip.co as an import.