exercicio6.js

const express = require('express')
const app = express()

const port = 3000

app.get('/somar', (req, res) =>{
    const sum = parseInt(req.query.num1) + parseInt(req.query.num2)
    res.send('A soma é: ' + sum)
})

app.listen(port,() => console.log('Serve running on port' + port))

Certinho.