Extract peptide information from proteomics data

Question

[Gene_MMP8]

I am just starting to learn how to analyze proteomics data. I have experimental results from a mass spectrometry experiment. It is a spectrum file containing only m/z and intensity values. I want to extract information (mass over charge) from the spectrum for a particular peptide whose chemical formula I know. How do I do that?

So far, I have derived the peak list for the given spectrum and then supplied the m/z values of the peak list to the MASCOT server (peptide mass fingerprinting). I would appreciate any help on how to proceed next.