You can see it if you open the in-game Store window, click on your login name in the upper right hand corner, and choose the drop-down option "History". This will open a page with all recent transactions. Depending on how much you have played since applying the code, you may have to scroll down a bit (past the DDO point grants for favor) to see the long list.
Or:
The coupon code grants the following quest packs:
Against the Slave Lords
Attack on Stormreach
Delera’s Tomb
Devil Assault
Disciples of Rage
Dragonblood Prophecy
Eveningstar Challenge Pack
Harbinger of Madness
Haunted Halls of Eveningstar
Heart of Madness
Keep on the Borderlands
Peril of the Planar Eyes
Phiarlan Carnival
Reign of Madness
Secrets of the Artificers
Sentinels of Stormreach
Shadow Under Thunderholme
Shan-to-Kor
Sorrowdusk Isle
Tangleroot Gorge
The Catacombs
The Demon Sands
The Devil’s Gambit
The Devils of Shavarath
The Dreaming Dark
The Druid’s Deep
The High Road of Shadow
The Lost Gatekeepers
The Mines of Tethyamar
The Necropolis, Part 1
The Necropolis, Part 2
The Necropolis, Part 3
The Necropolis, Part 4
The Path of Inspiration
The Reaver’s Reach
The Red Fens
The Restless Isles
The Ruins of Gianthold
The Ruins of Threnal
The Sharn Syndicate
The Soul Splitter
The Temple of Elemental Evil
The Vale of Twilight
The Vault of Night
Three-Barrel Cove
Trials of the Archons
Vaults of the Artificers
White Plume Mountain & Other Tales
(from
https://ddo.com/en/ThankYou)
What you do NOT get is the expansion packs: Menace of the Underdark, Shadowfell Conspiracy, Ravenloft, Sharn, Feywild and Saltmarsh.
You can get access to the quests in the first three in that list for 99 DDO points each for a limited time (until Dec 31st this year), which is also definitely worth getting.