Access the file build.gradle located in: NomeDeSeuProjeto/android/app/build.gradle.

locate the following code block

defaultConfig {
       // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
       applicationId "SeuAppId"
       minSdkVersion 16
       targetSdkVersion 29 // Modify here the value to 30
       versionCode flutterVersionCode.toInteger()
       versionName flutterVersionName
   }