Hi,
Are you trying to read pcap files from the file system? If so use suricata -r [path to file]
If you are using TZSP to send the traffic to another machine, sniffer with streaming-server set, then you need a tool to create data Suricata can parse from the TZSP stream.
Quick finds on google:
http://www.mikrotik.com/download/trafr.tgz