How to get a div knowing the class name from Element.classList in Javascript

I have this variable var which has a classList with some classes. Let’s say there is a class in there called “ssp“. How can i get this class only having the var and knowing the name of the class.
I can imagine that it should ne something like var.classList.get("ssp") and in my mind the get() function should return the element but I don’t think there is such method. So does anyone know how to do this?

In my case this is my code:

function newOption(father) {
    // here there should be this 'questionaire' div which has a classlist and one of those is called 'question'
    var father = document.getElementById('questionaire').classList.item(); // here i am trying to access it

    // here i am just adding another class to the father
    const op = document.createElement('div');
    op.classList.add("option");
    op.innerHTML = '<div contenteditable="true">Option</div><input type="checkbox" class="box">';
    father.appendChild(op);
}