"I want this for free" doesn't help either, just sounds like "Make my server for FREE" you can buy such code, you just waste your time if you dont like help.
"if someone just can copy-paste or even write some lines of code here" i just told you where to look at, if you cant do such simple search in your project maybe abandon the idea in general.
The admin command you've quoted demands to be online with one character to access some World/Player instances that one script alone can't. I don't have enough Java knowledge to be able to guess in an instant what all the code instances do and how they impact the final result, but I'm trying my best.
Also, I don't "just want for free": my intention is to compose the script and share it here the same way I did with the item delivery system by mail (which I only later found out already exists in the serverpack).
If you don't feel like collaborating that's fine, everyone is free to do as they please. But coming here to criticize and assume the intentions of others is highly toxic and unnecessary behavior.
PS.: about "paying", I intend to find a way to buy my access to become a subscriber soon and have the most up-to-date project... as soon as Mobius decides to unban me from Discord.