You'll never find these values from the datasheet. The datasheet shows the tranfer and saturation characteristics instead. If you need SPICE parameters for hand calculation or simulation, you must try and get the appropriate SPICE model from the manufacturer. Also, simulation tools like PSPICE or LTSPICE possess models of generic devices.
BTW: With an nMOSFET in common source configuration you can only control the negative path (low side) of the power supply. You could, however, use an nMOS in common drain configuration (i.e. as source follower) to control the positive path (high side), but then it won't be an LDO (Low Drop Out) controller. For an LDO controlling the high side, you'd need a pMOS.