CubeCell: Confirmation for Uplink?

How can I check in my code if my message reached a Lorawan Gateway? If sending was not successful, I would store the date and retry sending later.

Thx.

Use confirmed uplink option.
The gateway will send an an ack back after a package is received

Thanks for the quick reply. The uplink option is turned on. How do I react to the outcome in my code?