1995 s10 p/u 4 wheel drive 4.3 L When In 2 Wheel Drive I Only Have Front Brakes In 4 Wheel High Or Low I Have 4 Wheel Brakes What Do I Need To Fix This ?

The front brakes are supposed to be the primary stopping brakes, the rears don't provide much because they'll lock up quick if you really call on them.
The 4WD engagement mechanically ties all the wheels together...if you only had 1 wheel braking, it would drag the other 3 wheels down in 4WD.