LOLOL You'd think this would work, wouldn't you, Keijen! But it turns out that you're totally wrong and living in the past ;-)
First level barracks now is Goblin Spotter, lvl 2 is Black Smoke Assassin, etc.
Celine, this may sound crazy, but you need to put in a ticket to Gree and let them know that this particular quest is no longer doable... Back in the day, before guilds and Raid Bosses, the barracks would yield incredibly low-level units such as the Foot Soldier with stats 1att/2def, but with all the stat inflation, Gree obviously changed the first level Infantry unit to the Goblin Spotter stats 80/132... as you can see, huge difference!
BTW, the only reason I know this is that I accidentally sold my freakin' barracks once cuzza all the damn popup windows, and I had to upgrade it to L10 again smdh