Why does Postman show "error 404" when I try to save data into my Mongo database? - model-view-controller

Question

I have three files in my MVC architecture for my app.
Models folder:
I have exported the Mongoose schema and model like so:
const User = mongoose.model("User", UserSchema);
module.exports = User;
2. Controllers Folder
I have the following code in my controllers file:
const addUser = require('./../models/clientmodel');
exports.addUser = async (req, res) => {
try {
const newUser = await new addUser.create(req.body);
res.status(201).json({
status: "success",
data: {
newUser
}
});
} catch (err) {
res.status(204).json({
status: 'fail',
message: err
})
}
}
3. Routes folder
const router = express.Router();
router
.route('/')
.get (userControl.add_user)
app.post(userControl.newTour);
module.exports = router;
Why do I get the 404 error message in Postman?
How do I inser a loop?
NB: I am new to programming and learning the MERN stack.
The following code works fine in one folder:
const express = require("express");
const userModel = require("./models");
const app = express();
app.post("/add_user", async (request, response) => {
const user = new userModel(request.body);
try {
await user.save();
response.send(user);
} catch (error) {
response.status(500).send(error);
}
});
app.get("/users", async (request, response) => {
const users = await userModel.find({});
try {
response.send(users);
} catch (error) {
response.status(500).send(error);
}
});
module.exports = app;
I would like to refactor the code in the MVC architecture. When I split the code into controller/route configuration, then things do not work.