Help To Start ReactNative

Hello,
Looking for some help on an issue where i get an error every time ::

F:\Files\EimanMJ\ReAct\eiman>react-native run android

Unrecognized command ‘run’
Run react-native --help to see list of all available commands

F:\Files\EimanMJ\ReAct\eiman>react-native run-android
Starting JS server…
Building and installing the app on the device (cd android && gradlew.bat install
Debug)…

Configure project :app
Observed package id ‘build-tools;28.0.2’ in inconsistent location ‘F:\Files\Eima
nMJ\app\Android\sdk\build-tools\android-9’ (Expected ‘F:\Files\EimanMJ\app\Andro
id\sdk\build-tools\28.0.2’)
Observed package id ‘platforms;android-28’ in inconsistent location ‘F:\Files\Ei
manMJ\app\Android\sdk\platforms\android-9’ (Expected ‘F:\Files\EimanMJ\app\Andro
id\sdk\platforms\android-28’)

FAILURE: Build failed with an exception.

  • What went wrong:
    Execution failed for task ‘:app:installDebug’.

com.android.builder.testing.api.DeviceException: No connected devices!

  • Try:
    Run with --stacktrace option to get the stack trace. Run with --info or --debug
    option to get more log output. Run with --scan to get full insights.

  • Get more help at https://help.gradle.org

BUILD FAILED in 2s
27 actionable tasks: 1 executed, 26 up-to-date
Could not install the app on the device, read the error above for details.
Make sure you have an Android emulator running or a device connected and have
set up your Android development environment:
https://facebook.github.io/react-native/docs/getting-started.html