Put your cursor at the end of the paragraph and press Shift + Enter, then Delete, or show hidden characters, select the pilcrow a the end of the paragraph and press Shift + Enter.
Actually, I have a whole list of paragraph breaks and I was hoping to replace all of them at one time. Can I accomplish that with GREP
Only if there is a pattern to the ones you want to replace that makes them unique from the ones you want to preserve.
suppose I want to replace all paragraph breaks in that story with manual line breaks - what's the GREP for that?
Would using the standard Find/Change be sufficient, rather than GREP? If so, find ^p and replace with ^n in the change field.
GREP codes for all special characters and functions can be found in the Help: InDesign Help | Find/Change
In this case, you'd want to change
Be aware that this will glue paragraphs together, with all consequences for its paragraph styles. I do this so rarely (and then only on unformatted text!) that I'm not even sure if it will apply the top paragraph style to the next paragraph, or the other way around.