Edit: It will be under My Documents -> SH3 -> Data -> cfg -> Careers -> "Your Name"
All player data is stored there. Best of luck mate!
Edit 2: Welcome to what SH3 should've been upon release! I hope you will find it as satisfying and thrilling as I and everyone that uses it does. If you manually collect data on your targets, may I suggest MaGUI's mod. It helps out greatly and works like a charm!