This isn't really something that you can simulate easily, and will require some hand-calculations although it's very difficult to be more specific without knowing what you're trying to design.
You will need to work out the masses of the moving bits (which you can get from Fusion), measure the centre of masses (if relevant to the design), again with Fusion. Then, you'll need to work out the friction losses on the moving bits, based on the materials at the interfaces and whether they're greased, etc. This will need some information from somewhere like Engineeringtoolbox.com
Once you have all that, you'll have an idea of the force required to move the parts, and can then use the diameter of your leadscrew/length of your actuator arm to calculate the torque required on the motor.
