10 times 3Volts is 30 Volts. 4 times 1.5 Volt battery is 6 Volts, so you are AT LEAST 24 Volts short of your target, probably more.
Can't be bothered working out the maths, but I suspect that your potentiometer will burn out. If you want to reduce brightness, moving the light further away is much simpler. Else turn off half of the LEDs for half brightness etc.
Why not use 'D' cell batteries? They will last longer and (may) work out cheaper.
First problem is the most fundamental. You just don't have enough volts!