Imagine how easy it would be to unpack if you already know where the majority of your things will go? Like the floor plan, this isn’t about having everything 100% set in stone. It’s to give you a realistic view of what you have (seeing it in print is a big eye-opener), and gives you an idea of how much, if any, additional storage you may need.
MAPPING: Marrying step 1 + 2, give all your things a home within the home keeping in mind how you want to function in your new space. Use a copy of your proposed floor plan to draw it out (use pencil).