document.getElementById('btn-submit').addEventListener('click', () => {
  for (let tr of document.querySelectorAll('#mytable tr')) {
    let src = tr.querySelector('.myclass2'),
        dst = tr.querySelector('.myclass1 input');
    if (dst)
      dst.value = src ? src.textContent : '';
  }
});

`<input type="date" name="oplata_do" value="2018-05-04" />`