<div class="info">
  <div class="info-inner">
    <div>
      <p class="quantity">2</p>
    </div>
    <div>
      <p class="square">63,2</p>
    </div>
    <div>
      <p class="floor">2</p>
    </div>
  </div>
  <button>Click</button>
</div>

<div id="form">
  <form action="" class="contact-info-form" >
    <input name="quantity" id="quantity" type="text" placeholder="Quantity" required="required">
    <input name="square" id="square" type="text" placeholder="Square" required="required">
    <input name="floor" id="floor" type="text" placeholder="Floor" required="required">
    <input name="name" id="name" type="text" placeholder="Name" required="required">
    <input name="phone" id="phone" type="text" placeholder="Phone" required="required">
    <button class="send">Send</button>
    </form>
</div>

<div class="info">
                <div class="info-inner">
                  <div>
                    <p  class="quantity">2</p>
                  </div>
                  <div>
                    <p class="square">63,2</p>
                  </div>
                  <div>
                    <p class="floor">2</p>
                  </div>
                </div>
                <button onclick="textInp()">Click</button>
              </div>

              <div id="form">
                    <form action="" class="contact-info-form" >
                      <input name="quantity" id="quantity" type="text" placeholder="Quantity" required="required">
                      <input name="square" id="square" type="text" placeholder="Square" required="required">
                      <input name="floor" id="floor" type="text" placeholder="Floor" required="required">
                      <input name="name" id="name" type="text" placeholder="Name" required="required">
                      <input name="phone" id="phone" type="text" placeholder="Phone" required="required">
                      <button class="send">Send</button>
                      </form>
                  </div>

<script>
function textInp(){
    var gg=document.querySelectorAll('input');
    var pp=document.querySelectorAll('p');
    for(i=0;i<gg.length;i++){
    if(gg[i].id==pp[i].className){
       gg[i].value=pp[i].textContent;
    }
         }

}

    </script>