The version of QGC is in the application title bar, the current version is QGC v3.2.4 (BlueRobotics-Rev2).
When did you purchase your ROV? If you purchased it recently, then the software installed on the ROV should be up to date.
There are two computers in the ROV: The autopilot running ArduSub, and the Raspberry Pi ‘companion computer’ running the ‘companion’ software.
The current version of ArduSub is 3.5.1. You can check the currently installed version on the Summary tab of the Vehicle Setup page in QGC.
The current version of companion is 0.0.10. You can check the currently installed version by going to 192.168.2.2:2770/system in a chrome or firefox browser.
The current update instructions are here.