Step 2 : In search box write the name of files extension that you want to extract from sub folders. In this case because this sub folders House, Rap and Rock contains only music files you need to write .mp3.
Step 3 : The results will show you .mp3 files from all sub folders that you have. Now use Ctrl+A to select all files or your mouse to select just some of them. After that do Right Click - Cut (or Copy in case that you wont only to copy files not to extract them).