I guess S2P refers to touchstone (s-parameter) files.
The only commonly understood meaning of CVS in the software field is Concurrent Versions System, a software versioning and revision control system. Probably not addressed here.
Do you mean S2P to CSV?
If so you can do so using Excel, Open Office is similar
File > Open > select All files and open the .s2p file
In text import wizard select Delimited then Next
Select space delimiter, you can leave Tab selected
Press next and Finish.
Copy the data you want and save as CSV.