How do i solve this node.js error when im calling it with jQuery?

Question

I have this assignment and I'm a bit stuck.

When I press the button on the site the console I get this error:

GET http://localhost:3000/getUser 404 (Not Found) jquery-1.12.4.js:10254

Can anyone tell me what I'm doing wrong? I am new to node and our teacher didn't even have any lessons on it just expects us to know it I'm thankful for any answers I get

Here is my code:

Script.js

$(document).ready(() => {

$("#btn_prijava").click( () => {
    $.post('getUser', (uporabnik) => {
        console.log("Works");
    });
});
});

app.js

var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
const fs = require('fs');

var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
const { request } = require('http');

var app = express();

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);
app.use('/users', usersRouter);

app.post('/getUser', (req, res) => {
    res.send("User");
});

app.listen(3000, () => {
    console.log("App je pognan");
});

module.exports = ap