Warehouse Chief Alder:
You don't remember how to be a Scavenger? If you want to be a Scavenger, you must have achieved at least level 20 and passed the appropriate test.
Your level is satisfactory, but you haven't passed the Scavenger test. If you want to take the test, speak with Collector Pippi in the Dwarven Village. Pass her test and she'll give you a proof. Bring it to me and I'll make you a Scavenger right away.