Hi @_martinareds, welcome to the forum 
That’s PX4 documentation, but the BlueROV2 runs ArduSub firmware (not PX4 firmware), so the specific parameters you’re trying to read don’t exist in the vehicle.
The How to Use the Blue Robotics Forums post includes a link to the ArduCopter attitude controller docs, which should be similar if not identical to how ArduSub is controlled (because the functionality is in an abstracted library that both firmwares use). Attitude control uses the ATC Parameters. On the general ardupilot docs site you will also find the position control docs, which tells you that the PSC parameters are what you’re after.
They can be found in QGC’s Tuning page by clicking the “Attitude Controller Parameters” and “Position Controller Parameters” buttons at the top, or on the Parameters page by searching for ATC_ and PSC_.
If you happen to want to do this, you could read all parameters and print/save the ones that have a param_id (name) starting with ATC_ or PSC_. It’s easier if QGC is not open at the same time, otherwise you’ll need to create an additional MAVLink endpoint in the vehicle to connect to via Pymavlink.