it's easy. It's just unclear where you want the data to be.
Your arduino cannot write anything on your PC hard drive directly (would be quite a security hole !!!) so you need to decide where the data will go.
it could go on the serial line to the Serial monitor and then it's saved as a file, or it could be saved on an SD card on your Arduino if you have one connected... it could be sent by Wi-Fi or ethernet or bluetooth or SMS ... all depends on what you want to do and what hardware is available with your arduino
Yeah just so it can be downloaded in a way. It's for a future product so the consumer has to be able to download it somehow. A file such as .txt would work. What are the options for an Arduino Uno?
maybe you don't realize that the arduino interface to the PC is simply a serial interface and any program (e.g. putty) that can connect to a serial interface can communicate with an arduino instead of using the serial monitor