OK so you say the pressure is 1 atmosphere. Since the boiling temperature of water is 100 C at one atmosphere, then your 150 C steam must be superheated steam at 1 atmosphere.
Now you can apply your specific heat equation to determine how much heat must be removed to reduce the temperature of superheated steam at 150 C, 1 atm., to saturated steam at 100 C, 1 atm. You will need an appropriate value(s) of $C_p$ for water vapor in the range 100 C – 150 C at 1 atm.
You will now have saturated water vapor at 100 C and 1 atm. You can the look up the specific enthalpy (kJ/kg) in the saturated steam table. Then you can calculate the heat removed in order to convert saturated vapor to saturated liquid.
Now you will again apply your specific heat equation to reduce the temperature from 100 C saturated liquid at 1 atm to to 0 C water at 1 atm.
Finally use the latent heat of fusion to convert the 100 g of water at 0C to 100 g of ice at 0 C.
Hope this helps.