Maybe this way:
Q=Q1+Q2
Q is the heat that u need to bring to melt the ice
Q1 is the heat that u need to bring to raise the temperature of the ice to 273K
Q2 is the heat that u need to bring to break the intermolecular forces (so that you get from ice, water)
Q you can calculate with the calorimeter, and the inicial temperature of ice (I marked it with x).
Q=mc(273-x)+mλ---> m=Q/(c(273-x)+λ)