How to connect mini jack output to arduino mini pro and send sound to it?
The Arduino Uno / Mini Pro is not really the right tool for the job. It has no native audio output such as a 3.5mm jack.

Having said that I am sure it can be done - but it won't be the best quality sound. I have no doubt that it can be achieved with one of the following methods:


using the tone() function.
by using a R-2R resistor ladder network and some sort of amplification circuit.


The Arduino Due and the Arduino M0 / M0 Pro both have inbuilt DAC's, meaning that they can output analog signals which can be used to drive a speaker circuit.

Another option is to use a Raspberry Pi which has a native 3.5mm audio jack.