How to fix Nodejs Express Backend, Vercel production deployment routes issue

I just deploy my Node Js Express backend server on vercel but i can't get all the router defined in the router.js file through index.js using app.use().

How do i fix that issue !?

my index.js file :

app.use("/Api", Routes);
app.get("/", (req, res) => {
res.send("<center> MPDAM Project Server is Running Fine ..  </center>");
});

my router.js file :

const UserController = require("../controllers/userController");

router.get("/Users", UserController.getAllUsers);
router.get("/SingleUser/:id", UserController.getSingleUser);
router.post("/NewUser", UserController.NewUser);
router.delete("/DeleteUser/:id", UserController.DeleteUser);
router.patch("/UpdateUser/:id", UserController.UpdateUser);
router.post("/UserLogIn", UserController.UserLogIn);

my vercel.json file :

{
  "version": 2,
  "builds": [
    {
      "src": "./index.js",
      "use": "@vercel/node"
    }
  ],
  "routes": [
    {
      "src": "/(.*)",
      "dest": "index.js"
    }
  ]
}