Basically yes - be sure it's a logic-level MOSFET (that can be switched with 5V logic - most require 10V). The 5V fan might run a bit fast on 9V - so you are adding a resistor to drop the voltage a bit? You would normally do that on the high side, and switch with a n-channel MOSFET or NPN transistor on the low side.
Is the fan a brushless motor BTW?
I need to check if the MOSFET is a 5 level logic - i got the tech spec for the mosfet bt got to read it ..
but im pretty sure its a 10 V logic. .
Yes wanna use the resistor to drop the voltage a bit. about the circuit it seems i will need an NPN transistor ?
What if . . Can i achieve the same with an SSR?? And i already have that at hand, with 5 volt logic and switch up to 250 vac . . can i run the FAN without the need to get an external 5V power supply for the FAN, can i use the 9 Vdc . .
Concerning the FAN, i got them from the real china market, no specs at all, with brand name RUNDA without model no :-( i need the cfm as well for some sizing work bt . .
But still i will like to control these through pwm with my arduino without hurting my pins, . . .