I need to find the enthalpy of a solution from a lab I did in class here's the only info I have:

50 mL of water @ 25 degrees C inside of a calorimeter
Poured in 3.004 g of an unknown salt.
The temperature dropped from 25 to 21 degrees C

I need to identify the salt via the enthalpy (in kJ/g) can anyone help?

Your lab book or textbook will give the formula for determining the heat of solution.
You have data for delta T, the mass of solute and can look up the heat capacity of water. After conversions you will have the heat of solution in kJ/g. There must be tables available to you that give enthalpies of solution for various compounds, The data will probably be in kJ/MOLE so you will have to convert mole weights to grams. Hint just do this for the compounds that COOL the solution. That will narrow the field.