Try this:
FindAndReplace( FindAndReplace( @{Entry_Description}, "\r\r", "\r"), "\r", "\n")
However, as you can see, it will change all double carriage returns into a single one, then change all single carriage returns (including the pair of carriage returns generated from your former double carriage returns) into a line feed. Is this really what you want to achieve?
It you want to change all double carriage returns into a single one, and change all single carriage returns (but not the former doubles) into a line feed, you may try something this like:
FindAndReplace( FindAndReplace( FindAndReplace( @{Entry_Description}, "\r\r", "sarahmagat"), "\r", "\n"), "sarahmagat", "\r")