How can I convert an integer string into Jacascript

Question

Hi Good afternoon I am learning to program in js I am actually quite new in the subject. I am trying to solve an exercise but the answer is not coming out right. I am not conseginto convrrter the answer. I believe I did everything right. Someone can help me?

Penalty system

Car Speed: Km Hour

    <div id="res">

    </div> 

    <script>

        function calcular(){
            var txtv = window.document.querySelector('Input#txtvel')
            var res = window.document.querySelector('div#res')
            var vel = parseInt(txtv.value)
            res.innerHTML=  'Sua velocidade é ${vel} Km Hora'

        }
    </script>

**bold text**