Grep your P-Mos and place a source for Vds and Vgs
Use a DC-Simulation for a nice sweep of Vds. Probe Ids
of your pmos with internal spice paramters or an additional
0V voltage source between Drain and Source. Choosing
different values for Vgs yields in different curves. You can
also add this directly to your simulation if your simulator
has something like an ALTER support. With ALTER you can
define an additional sweep during the DC sweep of Vds.
Proper setup results in the well known IV characteristic
you're propably looking for