Generate a table using String and innerHTML template

Question

In one exercise, I was trying to create a table through DOM using template string and the innerHTML command

Where I want to insert the td

<tr id="boletinAluno">

</tr>

Creating the student

function cadastrarAluno(e){

    let nome = document.querySelector('#nome').value
    let nota1 = document.querySelector('#nota1').value
    let nota2 = document.querySelector('#nota2').value
    let nota3 = document.querySelector('#nota3').value

    let aluno = new Aluno(nome,nota1,nota2,nota3)

    montarLinha(aluno);



}

Montarlinha

function montarLinha(aluno){
        let content = `
        <td>${aluno.nome}</td>
        <td>${aluno.nota1}</td>
        <td>${aluno.nota2}</td>
        <td>${aluno.nota3}</td>
        <td>${aluno.getMedia}</td>

        `
       boletin = document.querySelector('#boletinAluno').innerHTML+=content;


    }

ERROR

index.html:89 Uncaught TypeError: Cannot read property 'innerHTML' of null
    at montarLinha (index.html:89)
    at cadastrarAluno (index.html:75)
    at HTMLInputElement.onclick (index.html:39)
montarLinha @ index.html:89
cadastrarAluno @ index.html:75
onclick @ index.html:39