Responsive Column Order is available in Column’s Advanced tab inside the “Advanced” option.
Find the “Responsive Column Order” option in Column:
In the section, click on the column icon to edit the column options. See below image:
Now in Elementor’s main panel (left side), click on “Advanced” tab from the top. Now see the “Responsive Column Order” option in the “Advanced” option. See below image:
Click on the desktop icon to expand the device options.
Define the order number for each device as your plan. Note that, you need to fulfill the process of each column inside of that section. By default, every column order has been set to “0” ((zero). If no value has been set then that column will appear in the first place. So after defining the all column order, you will get the expected result.