When you go to Gorn to start the quest to free the Free Mine, he'll send you back to talk to Wolf. Accept Wolf's ingenious idea of using minecrawler shell plates to make an armor and agree to collect a few while killing everyone in the Free Mine.
Once in the Free Mine, you'll only find minecrawlers in specific parts. In the first chamber, there is the entrance to a small cave at the bottom-left and there are 2 minecrawlers therein. Further into that cave is a drop-off into a pit with another 2 minecrawlers. In the second chamber of the Free Mine, there are 2 minecrawlers at the bottom of the huge pit. Finally, in the room with Tarrok, the Orc slave, there are 5 minecrawlers. The total number of minecrawlers in the Free Mine, therefore, is 11, and each has two plates to harvest.
Back in the New Camp, Wolf won't take all of your minecrawler plates, he'll only take the 15 he'll need to fashion the armor. You can sell the rest.
Return to Wolf once you have completed "Search for the Ulu-Mulu", the armor won't be complete until then.