Samsung Galaxy S5: Settings > About device > Build number.Stock Android: Settings > About phone > Build number.Finding it can be different depending on the device:

To do this, navigate your phone to the “Build number” portion in your device’s Settings. To enable USB debugging, you first need to enable Developer options. USB debugging is a useful way to debug while connecting your Android device to the SDK, so get this set up before moving on to the next step. In step 4 of Installing the SDK, be sure to add at least one Android platform with API level equal to or higher than 9 (Platform 2.3 or greater), the Platform Tools, and the USB drivers if you’re using Windows. You can skip the optional sections relating to Eclipse. Install the Android SDKįollow the instructions in Installing the SDK. Download and unpack the latest Android SDK. On your PC, go to the Android Developer SDK website. Whether you’re building an Android application in Unity or programming it from scratch, you need to set up the Android SDK (software development kit) before you can build and run any code on your Android device.

Update android sdk