Before you can transfer a volume from one droplet to another, you need to detach the volume from droplet one. Attempting to attach it first, heres what it outputs:

doctl compute volume-action attach 72850d10-7cec-11ef-951c-0a58ac120368 447964468

Error: POST https://api.digitalocean.com/v2/volumes/72850d10-7cec-11ef-951c-0a58ac120368/actions: 422 (request "9472baea-dfbb-41f7-abfa-89c7c4112c9a") error attaching volume to droplet: storage already associated with another droplet

It would be good if the doc shows you how to safely detach the volume from droplet 1.