You can open my file attached and it will open a package including input file, workflow and output. You can change the path to input/output. You can drop new file for conversion and keep the original for the mappings dictionary. I created another example for you.
In the input Data tool I hard coded the start line and the end line for now. Also, when you change data you might adjust the formula for calculations. Otherwise to make the workflow more universal you can cancel flag "Take column names from first row" and then you will work with Column1-Column2-Column3. Great questions - I think with a little play you will figure it out.