How to run `npm react-native run-ios` after upgrading mac os and upgrading xcode?

I picked up a react-native project from 2018. I was able to get the app to work in a simulator by typing npm install; npx react-native run-ios on a 2012 mac mini that had Xcode 9.0 installed.

However, the iPhone 11 was not available from the list of simulators. I read that I needed Xcode 11+ to get iPhone 11 simulator. So i upgraded my mac mini from OS 10.13 to OS 10.15, then I upgrade Xcode to version 12.0.

I loaded up the new Xcode and entered my Apple ID. I then went to terminal and typed npx react-native run-ios, but I got the error:

`instruments` is now deprecated in favor of 'xcrun xctrace' (see `man xctrace` for more information on its replacement)Could not find iPhone 6 simulator

So then I ran the command rm -rf node_modules; npm install;, but then I got the error:

npm ERR! error: pathspec 'master' did not match any file(s) known to git

And trying to run npx react-native run-ios gives the error:

Command `run-ios` unrecognized. Make sure that you have run `npm install` and that you are inside a react-native project.

How do you make npx react-native run-ios to work?