Samsung galaxy tab 7.0 plus Kies firmware update problem (reply and help ASAP)

[AC Question]

I'm using GT-P6200 (samsung galaxy tab 7.0 plus) i was updating its firmware using samsung kies on computer .Then on my tablet it says firmware update encountered an issue please select recovery mode on samsung kies and try again . I instantly clicked ok for the code and I panicked . Then i unplugged the usb cable . Now I'm stuck on the firmware upgrade encountered an issue .Please help as i have decided to not update its firmware . I want my tablet to go back to normal . I've tried to push the volume up and power button and even tried to push the volume down and power button but Its stilll the same .Plus when i tried to connect back the usb cable , my computer said USB not recgonised .