I have a Samsung tablet 3 7" running on 4.2.2 (T-Mobile) , I loaded some MP3 files on the micro SD card but couldn't find the media player app in Apps folder to play the music ? Thanks
Will try that. Another thing though , my son has an exact tablet but with Sprint , his has the app to play music (I think this app called "music") and mine does not ? Can I install this app from "play store" ?
There are plenty of media players on the Play Store that should do what you want. I personally have Google Music on my tablet, since it not only plays local files, but your files stored on Google's servers. There are many others that don't have cloud integration.
Outside of the Play Store, f-droid.org has media players, including the stock music app included in Android. Amazon has many media players as well.