Google up XDA Developers.
Be aware that they may be very rough on you. That is, there are tomes on this one.
Okay, I'm trying to unbrick my friend samsung tab 3 t210. He tryed rooting it and messed up, leaving it witrh a soft brick. I have tried several solutions of unbricking it with no success. The tablet still boot loops, or hangs on the screen. It also says about unable to mount data. If you have any solutions I could try, let me know. Thanks