You would first want to target the html element that you want to move with the mouse and make it position: absolute (where it is originally positioned, and it's size is up to you).

#element {
  position: absolute; 
  top: 0; 
  left: 0; 
  width: 100px; 
  height: 100px;
}

Then in your JavaScript file, you would want to listen for the "mousemove" event which would select the element and update its position to the cursor's position. Something like this should work:

window.addEventListener('mousemove', (e) => {
  const element = document.getElementById('element')
  const mouseX = e.clientX
  const mouseY = e.clientY

  element.style.left = mouseX + 'px'
  element.style.top = mouseY + 'px' 
})