website design – Mapping of column fields from CSV file with currently available fields

You can try really intuitive like Match the following which we have done in our childhood.

i can suggest you few interactions but you have to be precise with visuals as if not properly visualised it may end up bad.

but make sure when you hover on a single item other lines(lines of other elements) will have opacity 50% so that they may not effect visibility
enter image description here

Here you just drag the item in the list1 and put it under item2 of other list.

enter image description here