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You can just use the equation Id = 0.5 Kn (W/L) (Vgs - Vth)2 (1 + λ Vds)
Do the simulation for Different Id, Vgs, Vds, You have two unknowns Kn and λ which you can then calculate.
These values will change with the operating conditions. λ will vary with Vds and Id and a lot of other parameters.
You might have to do a bunch of simulations and get a bunch of values. You can take a average of them or keep all the values and use each when when required.
If Ro or Rds or Gds of a transistor is provided in the dc operating point solution, you can use the equation Ro = 1/(λ*Id)