First calculate your speed / torque requirements, and decide if it fits within the range of a stepper motor.
(With stepper motors usefull torque tends to fall a lot abouve 600rpm).
If your lead screw only needs to rotate very slowly you can add some gears or a timing belt, which results in less needed torque for the (stepper) motor.
Then go to some site where you can buy stepper motors, get some datasheets and see if they fit your requirements.
If the first fails to meet them, get a datasheet of a bigger motor, if the motor has muh more torque capability then you need, get a smaller motor.
"Usefull" torque of stepper motors also depends a lot on the quality of the motor driver and the supply voltage for that driver.
Steper motors & driver combinations with built in position feedback are also becoming more common nowaday's.
With position feedback you need less torque reserve for the motor, which can result in a smaller motor, which pays for the feedback components. With position feedback the driver also dynamically adjusts the motor current, which results in higer efficiency and less mechanical vibrations and noise.