Grid

place-items

justify-items => Horizontal Axis Align
align-items => Vertical Axis Align

place-items: <align-items> <justify-item>

CSS
.container {
  display: grid;
  height: 600px;
  grid-template-columns: repeat(3, 1fr);
  place-items: center start;
}
Box-1
Box-2
Box-3
Box-4
Box-5
Box-6
Box-7
Box-8
Box-9
CSS
.container {
  display: grid;
  height: 600px;
  grid-template-columns: repeat(3, 1fr);
  place-items: center;
}
Box-1
Box-2
Box-3
Box-4
Box-5
Box-6
Box-7
Box-8
Box-9