npｍのインストールが上手くいかない

@ start /Users/user/my-react-app/my-react-app

react-native start

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             Welcome to React Native!
            Learn once, write anywhere

To reload the app press "r"
To open developer menu press "d"

shimoda-no-MacBook-Air:my-react-app user$ npm run android

@ android /Users/user/my-react-app/my-react-app
react-native run-android

info Running jetifier to migrate libraries to AndroidX. You can disable it using "--no-jetifier" flag.
Jetifier found 1277 file(s) to forward-jetify. Using 4 workers...
info Starting JS server...
/bin/sh: adb: command not found
info Launching emulator...
error Failed to launch emulator. Reason: No emulators found as an output of emulator -list-avds.
warn Please launch an emulator manually or connect a device. Otherwise app may fail to launch.
info Installing the app...
No Java runtime present, requesting install.

error Failed to install the app. Make sure you have the Android development environment set up: https://reactnative.dev/docs/environment-setup. Run CLI with --verbose flag for more details.
Error: Command failed: ./gradlew app:installDebug -PreactNativeDevServerPort=8081
No Java runtime present, requesting install.
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @ android: react-native run-android
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the @ android script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /Users/user/.npm/_logs/2020-08-11T09_39_44_369Z-debug.log
shimoda-no-MacBook-Air:my-react-app user$ npm run ios

@ ios /Users/user/my-react-app/my-react-app
react-native run-ios

error Could not find "Podfile.lock" at /Users/user/my-react-app/my-react-app/ios/Podfile.lock. Did you run "pod install" in iOS directory?
error Could not find the following native modules: RNGestureHandler, RNReanimated, RNScreens. Did you forget to run "pod install" ?
info Found Xcode project "myreactapp.xcodeproj"
xcrun: error: unable to find utility "simctl", not a developer tool or in PATH
error Could not get the simulator list from Xcode. Please open Xcode and try running project directly from there to resolve the remaining issues. Run CLI with --verbose flag for more details.
Error: Command failed: xcrun simctl list --json devices
xcrun: error: unable to find utility "simctl", not a developer tool or in PATH
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! @ ios: react-native run-ios
npm ERR! Exit status 1> 引用テキスト
npm ERR!
npm ERR! Failed at the @ ios script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR! /Users/user/.npm/_logs/2020-08-11T09_40_00_683Z-debug.log
shimoda-no-MacBook-Air:my-react-app user$ a
-bash: a: command not found
shimoda-no-MacBook-Air:my-react-app user$