Add the following dependencies to your `pubspec.yaml` file and install dependencies when asked. Please keep in mind that Auth plugin is needed for IAM authorization mode, which is default for REST API:

```yaml
environment:
  sdk: ">=2.18.0 <4.0.0"

dependencies:
  flutter:
    sdk: flutter
  amplify_flutter: ^1.0.0
  amplify_api: ^1.0.0
  amplify_auth_cognito: ^1.0.0 
```