Reactjs – why when i Deploy in vercel MERN APP shows me Error 404?

I’am trying to deploy my backend mern app in vercel and it shows me this error :

"404: NOT_FOUND
Code: NOT_FOUND
ID: cdg1::bbhc7-1691147707623-efc5cd10ff98

Here is my server.js file:

require("dotenv").config();
const express = require("express");
const mongoose = require("mongoose");
const cors = require("cors");
const cookieParser = require("cookie-parser");
const SocketServer = require("./socketServer");

const app = express();
app.use(express.json());
app.use(cors());
app.use(cookieParser());

// Socket
const http = require('http').createServer(app);
const io = require("socket.io")(http);

io.on("connection", socket => {
SocketServer(socket);
});

app.use("/api", require('./routes/authRouter'));
app.use("/api", require('./routes/userRouter'));
app.use("/api", require('./routes/postRouter'));
app.use("/api", require('./routes/commentRouter'));

const URI = process.env.MONGODB_URL;

mongoose
.connect(URI, {
useNewUrlParser: true,
useUnifiedTopology: true,
})
.then(() => {
console.log("Connected successfully to MongoDB");
})
.catch((err) => {
console.error("Error connecting to MongoDB", err);
});

const port = process.env.PORT || 5000;
http.listen(port, () => {
console.log("Server is running on port: ", port);
});

And here is my backend’s package.json:

"scripts": {
"dev": "nodemon server.js"
},

What should I do, please? Thank you.

help me please to find the solution