Custom curcit help that has 3 components (Mic/Transistor/motor)
Divide this project into three sub-modules:


Standard microphone pre-amp (amplifier) circuit, including bias if using an electret microphone. Output should be AC-coupled through a non-polarized series capacitor. Test by measuring amplitude using oscilloscope.
Comparator to detect when sound amplitude exceeds a preset threshold. You may need to use a low-pass filter and diode peak detector before the comparator. Depending on how precise you expect this thing to be, you may need a voltage reference, or go cheap and just use a trimmer potentiometer. Use hysteresis (positive feedback) to make the "off" threshold different from the "on" threshold. Test by using an audio function generator, ramping the amplitude up and down, and measuring input and output on oscilloscope.
Motor driver circuit controlled by the comparator output. An NPN transistor with a heatsink, along with a freewheeling diode to block back EMF, would be a good place to start. Test by pulling the NPN base low. (If you are using a comparator with open-collector/open-drain output, you need a pullup resistor for the high state.) 


Each of those sub-modules should be constructed and tested separately. You didn't indicate in your question whether you've ever built anything before, or what tools you have available. But I would assume you have at least a soldering iron, a DMM, and an oscilloscope, otherwise you won't be able to determine whether the sub-modules are working correctly. An audio function generator would be useful for testing the comparator independently of the mic preamp.

I wouldn't bother attempting to build this on solderless breadboard, because the mic preamp and the comparator will be adversely affected by the parasitic inductance and capacitance. I'd go directly to one of those pad-per-hole blank prototyping breadboards, like the ones that are all over ebay.

If it doesn't perform as you expect, you might need to insert some additional filtering between the mic preamp and the comparator. The microphone's sensitivity may not be aligned with human hearing sensitivity, and so your device might have unwanted response to sounds you're not generally aware of, such as audible 60Hz/120Hz/180Hz hum due to the power mains or a 20kHz ultrasound above your range of hearing. So you may want to add a bandpass filter to pass the 1kHz to 3kHz range, for example.