Making a DC motor turn in saturation and cutoff modes of an NPN transistor
A MOSfet control element might be more appropriate than a bipolar transistor:

Since the specification of the light-dependent resistor is missing, R1 might have to be chosen differently to set the light threshold where the MOSfet turns on, and the motor starts turning.
In the simulation, a small DC motor is assumed, that requires a few hundred milliamps. Its resistance is estimated at 30 ohms. The 9V battery may be too feeble to handle this load.






simulate this circuit &ndash; Schematic created using CircuitLab
Recall that light-dependent resistance has an inverse relationship to light level. Dark resistance is high, often larger than 1 MEGohm. Bright light may reduce resistance to hundreds of ohms.

In this circuit, motor current starts flowing when LDR1 is about 10K ohms. Gain is fairly high - this MOSfet almost acts as a switch - its linear region is quite small, where LDR1 ranges between 10k-to-12k. This helps to keep M1 cool. But linear region is probably large enough that a flyback diode (across the motor) isn't necessary.