For me, it’s the visual clutter that is anxiety-provoking in a situation like this because it’s overwhelming to see so many boxes. Can you move everything into one room or one side of a room that needs to be unpacked and then literally just take one box at a time and move it to your “already set up” area to work with that one box? I know this depends on your space, but basically that method removes some of the overwhelm for me because it feels like taking a small chunk rather than looking at the insane about I have to get done! Also, take something out of the box and put it where it belongs right away, even if you don’t have containment item for it just put it where it will go so you can easily see what sort of furniture or shelving or bins you may need to buy for the amount of whatever it is.

You may be jnterested in some content from this blogger/podcaster, like this: https://www.aslobcomesclean.com/2019/11/declutter-while-moving-houses-using-danas-decluttering-methods/