Appending text files to other .txt files

Job ID: 30715944

Budget: $30 – $250 USD

We have two folders - like the ones attached, stocksOne and NewStockData - each consisting of various sub-folders that contain .txt and .csv files (we ignore the .csv files).
As you can see, the subfolders in the two 'master' folders bear same names, say StocksUSA-11hour in the first and the same (StocksUSA-11hour) in the other as well, and they both contain .txt files of same names also, say AAPL.txt in one and AAPL.txt in the other
I just want a software that runs fast of course and APPENDS the contents of every .txt file of the first folder (after a certain row there...we will discuss) at the bottom of its corresponding .txt file in the other folder.