Go to the correct folder of your project:

cd path/to/MyProject

Install the dependencies:

npm install

Or use Yarn:

yarn install

Install React Native CLI (globally):

npm install -g react-native-cli

Start the Metro Bundler manually:

npx react-native start

And in another terminal:

npx react-native run-android

Clean up the project (optional):

npx react-native clean npm install npx react-native run-android

If the problem persists, try removing your node_modules and package-lock.json and run npm install again.