You can do this from your WHM --> Transfers --> Copy multiple accounts from another server
Give the IP of the server from which you want to copy.
If you have direct root login, check root against login user
Check password as authentication method and give the password.
Now click on fetch account list.
On next page, you will see all accounts in the remote server.
You can select your reseller account and all accounts under it and WHM will do the rest.
sojish, you just beat me.