How to get list variable row size?

I have a list variable called metrics which has multiple entries as rows under its column metricName. I'd like to loop through all the values in that column. So loop for each row in the metricName column. I want to use the loop logical action so that I could loop through all the row values in a single iteration.

Since loop action counter requires us to define how many times we want to execute the loop, I'd like to pass total number of rows in my list variable as a value to that parameter in loop. Is there a "size" or "length" attribute in list variable to determine the number of rows?