About form submission

Hello campers…
I have a html form I validated with html validation. I want it to be able to submit with just javascript and html and redirect to a confirmation page I created for it. Please how can I achieve this.

html

 <form action="/confirm.html"  method="post" id="form">
        <ul>
            <div class="aligned">
                <li class="item">
                    <label for="name" class="aligned-label">First name *</label>
                    <input type="text" class="aligned-input" id="fname" name="user_firstname" required>
                </li>
                <li class="item">
                    <label for="name" class="aligned-label">Last name *</label>
                    <input type="text" class="aligned-input" id="lname" name="user_lastname" required>
                </li>
            </div>
</ul>

<input type="submit" value="Submit">
</form>