Find password for Linksys spa2102

Does anybody have any idea how I can find the password for a Linksys spa2102. I have tried to use the spa2102-r sniff.pcap. and the sniff w static ip.pcap. but they have not shown the user name and password. I am using a new fritzbox router so would this be stopping me from having access to this information. I would be grateful if anybody could tell how to set up the wireshark to find this data for me.