Hey Tenjin,
Can I get you to make a ticket via the complex ftb discord so that we can better help you? It will be easier and faster for us to get you a refund of the item that way. There are details on how to make a ticket in the #help-and-support channel channel.
Discord:
Discord.gg/complexftb
You use
/is expand 1
You can use it several times as long as you have the claim blocks for it but the max size of an island is 128x128. You can find the current size of your island by running
/is info
You can also edit the number in the command so you dont run it so many times but it wont go...