Change version and code version number Android Studio

In build.grandle write

android {
    signingConfigs {
        release{
            keyAlias 'myalias'
            keyPassword 'somepass'
            storeFile file('C://Keystore/my.keystore')
            storePassword 'somepass'
        }
    }

    defaultConfig {
        applicationId '/com/....myapp.apk'
        minSdkVersion 9
        targetSdkVersion 26
        versionCode 30
        versionName '19.3'
        signingConfig signingConfigs.release
    }
}