Solution1:
• While developing, as you’ll be aware of required fields so you can add the asterisk symbol directly:

.xml file:-
<div class="form-group field-confirm_password">
<label for="confirm_password">Confirm Password *</label>
<input type="password" name="confirm_password" id="confirm_password" class="form-control form-control-sm" required="required"/>
</div>

Solution2:
You can call the Js file where #register is your id of the form, find out the input tags having property ‘required’.

.xml file:-
<input type="password" name="confirm_password" id="confirm_password" class="form-control form-control-sm" required="required"/>

.js file:-

$('form#register').find('input').each(function() {
if ($(this).prop('required')) {
$(this).addClass("required");
}

});
.css file :-
.required:after {
content:" *";
}

Thank you bro!
It's exactly what i need.