boot – how to delete a partition(sdb6) that is ordered before the root partition (sdb7)

Recently I has been struggling with updating from Ubuntu 18.04 to Ubuntu 2.04, and I ended up installing a new os. now I have my old root partition as /dev/sdb6, and I formatted it, and I want to use it to extend the current root partition (/dev/sdb7). but it’s hard as it’s before the current root in order. Any help how can I do this ? enter image description here