How do i choose all Non-air blocks in a procedure?

i want to make a jetpack, which gives you slow-falling when you are 3 or 4 blocks in the air, but i want to use all non-air blocks for that, how do i do this?

i want the item in the red circle to be the all non-air blocks
could anyone help with this?

(if the image doesnt work: https://imgur.com/a/OpVLTd0)