"- Node version not specified in package.json" while hosting on heroku - node.js

Question

I have a MERN project that I want to host on Heroku, but while deploying it I'm getting an error:- "Push rejected, failed to compile Node.js app. Push failed". below is the package.json file of the server/backend :-
{
"name": "backend",
"version": "1.0.0",
"description": "Blog-Application",
"main": "app.js",
"type": "module",
"scripts": {
"start": "node app.js",
"heroku-postbuild" : "NPM_CONFIG_PRODUCTION=false npm install --prefix client && npm run build --prefix client"
},
"author": "",
"license": "ISC",
"dependencies": {
"alert": "^5.0.10",
"bcryptjs": "^2.4.3",
"cors": "^2.8.5",
"express": "^4.18.1",
"mongoose": "^6.3.2",
"nodemon": "^2.0.16",
"popups": "^1.1.3"
}
}
I checked package.json but didn't find any mistake(Taking reference to some videos)...but when I'm running this command:-
git push heroku master
this is showing me:-
Enumerating objects: 61, done.
Counting objects: 100% (61/61), done.
Delta compression using up to 4 threads
Compressing objects: 100% (59/59), done.
Writing objects: 100% (61/61), 1.25 MiB | 235.00 KiB/s, done.
Total 61 (delta 1), reused 0 (delta 0), pack-reused 0
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Building on the Heroku-20 stack
remote: -----> Determining which buildpack to use for this app
remote: -----> Node.js app detected
remote:
remote: -----> Creating runtime environment
remote:
remote: NPM_CONFIG_LOGLEVEL=error
remote: NODE_VERBOSE=false
remote: NODE_ENV=production
remote: NODE_MODULES_CACHE=true
remote:
remote: -----> Installing binaries
remote: engines.node (package.json): unspecified
remote: engines.npm (package.json): unspecified (use default)
remote:
remote: Resolving node version 16.x...
remote: Downloading and installing node 16.15.1...
remote: Using default npm version: 8.11.0
remote:
remote: -----> Installing dependencies
remote: Installing node modules
remote:
remote: added 211 packages, and audited 212 packages in 4s
remote:
remote: 29 packages are looking for funding
remote: run `npm fund` for details
remote:
remote: found 0 vulnerabilities
remote:
remote: -----> Build
remote: Running heroku-postbuild
remote:
remote: > backend#1.0.0 heroku-postbuild
remote: > NPM_CONFIG_PRODUCTION=false npm install --prefix client && npm run build --prefix client
remote:
remote: npm ERR! code ENOENT
remote: npm ERR! syscall open
remote: npm ERR! path /tmp/build_cf8c0d20/client/package.json
remote: npm ERR! errno -2
remote: npm ERR! enoent ENOENT: no such file or directory, open '/tmp/build_cf8c0d20/client/package.json'
remote: npm ERR! enoent This is related to npm not being able to find a file.
remote: npm ERR! enoent
remote:
remote: npm ERR! A complete log of this run can be found in:
remote: npm ERR! /tmp/npmcache.aw0ai/_logs/2022-06-13T18_00_08_638Z-debug-0.log
remote:
remote: -----> Build failed
remote:
remote: We're sorry this build is failing! You can troubleshoot common issues here:
remote: https://devcenter.heroku.com/articles/troubleshooting-node-deploys
remote:
remote: Some possible problems:
remote:
remote: - Node version not specified in package.json
remote: https://devcenter.heroku.com/articles/nodejs-support#specifying-a-node-js-version
remote:
remote: Love,
remote: Heroku
remote:
remote: ! Push rejected, failed to compile Node.js app.
remote:
remote: ! Push failed
remote: Verifying deploy...
remote:
remote: ! Push rejected to blogsite07.
remote:
To https://git.heroku.com/blogsite07.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/blogsite07.git'
Please help me, where I'm doing wrong.