Record collection to string ('Write file' flow fuction)

I want to save a ‘record collection’ of a data variable to one file. I have figured out how the ‘write file’ flow function works just not yet how I can save a ‘record collection’ to one file.

My idea was to “convert” it to a string but I cannot figure out how. Anyone ideas?

I guess that what you are looking for is this formula right here:

So what you would do is: