Not able to build downloaded code

[cyeh1234]

Did a Flutter pub get
got the following message

Tried to update pubspec.yaml to

name: flutter_clean_architecture
description: Example project using clean archtecture on flutter
version: 1.0.0+1

environment:
sdk: ">=2.7.0 <3.0.0"

dependencies:
flutter:
sdk: flutter
shared_preferences: ^0.4.2
cupertino_icons: ^0.1.2
json_annotation: ^4.4.0
flutter_mobx: ^2.0.3+2
injectable: ^1.0.0
http: ^0.13.4
get_it: ^4.0.2
mobx: ^2.0.6+1

dev_dependencies:
flutter_test:
sdk: flutter
injectable_generator: ^1.5.2
json_serializable: ^6.1.3
mobx_codegen: ^2.0.5+2
build_runner: ^2.1.7
mockito: ^5.0.17

flutter:
uses-material-design: true
assets:
- assets/json/

Got the following message