Unable to resolve bare specifier 'vue-router'

I have a micro-frontend project using vue 3. I have done yarn install and yarn serve:standalone. But I have an error like this

this is my vue.config.js

module.exports = {
  lintOnSave: false,
  configureWebpack: {
    devServer: {
      headers: {
        "Access-Control-Allow-Origin": "*",
      },
      disableHostCheck: true,
      sockPort: 9003,
      sockHost: "localhost",
      https: true,
      port: 9003,
    },
    externals: ["vue-router"],
  },
  filenameHashing: false,
};