DC motor control using BJT
Some things you are going to have to resolve. 


The motor you linked runs on 12 to 24V. Not the 3V you show in your proposed circuit.
The 2N3904 NPN transistor is unsuitable for this application. They are typically good for up to ~200mA whilst the motor specs a load current of 300mA and that will grow as more load is placed on the motor.
A resistor in series with the motor is not really going to work. You need to let the motor windings limit the current and then pick a transistor (hopefully a MOSFET) that can handle the current.
When driving an inductive load with active switching you surely need a flyback diode across the motor or else the inductive kick at the turn off time will kill your transistor.
Use a MOSFET and you can limit the amount amount of current load on the Arduino output. 


Ok @elecstud ... ball is in your court now.