We are given an assigment about mosfet common source amplifiers and we are given this circuit. I drew its small signal equivalent circuit but I am so unsure about placement of ro(transistor resistor). Can you tell me if it is correct or not and help me if it is not correct
This is correct small signal model of a common source MOSFET amplifier. You’ve placed Ro correctly across drain and source terminals. Also your input impedance would simply be R1||R2 while your output impedance is RD||(1+ gmRs)Ro. This is a little more complex to derive but can be done with circuit analysis.
See this link for Analysis: I/O Resistance of common source MOSFET with source degeneration
Note: I used Microelectronic circuits 6th sedra/Smith so they approximate output resistance as RD||(1+ gmRs)Ro.