I do not think there is any specific command to simulate 1/f noise ONLY. What you can do is to do a noise analysis (AC or PSS), start with very low frequency, then you should be able to see the 1/f noise contribution at low frequency depends on your biasing of your MOSFET
If you use Cadence Spetre to do the noise analysis, choose the "frequence" as the "sweep variable". After the simulation, you can choose the “Results”->“Print"->"Noise Summary”.Then a "Noise Summary" window will appear. after filling the form, it will show all the noise in the schematic, the flick noise will have a symbol as "fn".
If you need more information about the "Noise" analysis, you can consult the documents of Cadence IC 5.141