What does [ERROR_MODULE_NOT_FOUND] mean?

After running “nodemon server,” I got this error:

[nodemon] 2.0.15
[nodemon] to restart at any time, enter `rs`
[nodemon] watching path(s): *.*
[nodemon] watching extensions: js,mjs,json
[nodemon] starting `node server index.js`
internal/process/esm_loader.js:74
    internalBinding('errors').triggerUncaughtException(
                              ^

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/Users/brandonkim/Desktop/restaurant-reviews/backend/server.js' imported from /Users/brandonkim/Desktop/restaurant-reviews/backend/index.js
    at finalizeResolution (internal/modules/esm/resolve.js:271:11)
    at moduleResolve (internal/modules/esm/resolve.js:694:10)
    at Loader.defaultResolve [as _resolve] (internal/modules/esm/resolve.js:805:11)
    at Loader.resolve (internal/modules/esm/loader.js:88:40)
    at Loader.getModuleJob (internal/modules/esm/loader.js:241:28)
    at ModuleWrap.<anonymous> (internal/modules/esm/module_job.js:72:40)
    at link (internal/modules/esm/module_job.js:71:36) {
  code: 'ERR_MODULE_NOT_FOUND'
}
[nodemon] app crashed - waiting for file changes before starting...

What does this mean? How do I fix it? I am just simply trying to run the server for the backend of a website.

My package.json is:

{
  "name": "backend",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "type": "module",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "bson": "^4.2.2",
    "cors": "^2.8.5",
    "dotenv": "^8.2.0",
    "express": "^4.17.1",
    "mongodb": "^3.6.4"
  }
}