Is there any app that convert any song into tab?

Currently not available. Even if available, the application will not be able to change a song that consists of many instruments.

The easiest way is to send us a request, let our musicians write the tab for the song you want.

Not that I know of, detecting melody lines from a track with multiple instruments would be very difficult.

But there is an app called Moises which detects chords with maybe 80% accuracy.

There are online services like https://guitar2tabs.com, but they are only available for the first 30 seconds.