Dear @CHAILIN,
Please see a previous forum question: Nuclear Data File Selection
In particular, the data for Co-60 source is taken from: https://www.sciencedirect.com/science/article/abs/pii/S0090375286801107
If you want to check it by running FLUKA, you should define a detector region and an associated USRTRACK (dE/dx) scoring. Note it is material dependent.
Let me know if there is anything I can help with.
Best,
Daniel