Testing an ETL

Hello.

Guys, I want to test my ETL by counting the rows of my initial "Table input" and, after the transformation and loading process are done, count the rows in my "Table output" and compare if the number is equal.

I guess is pretty easy but I haven't managed to do it by now... I see there is a tool under "Utility" that says Table Compare, but I also haven't managed to use it correctly, apparently.

Thanks for the replays.