How do I compare 2 PCAP files in Wireshark?

edit

Need more details what you are trying to accomplish and packet count. The packets may not be the same order. It depends on the protocol, full duplex, and latency. Example is TCP busy session with 16ms latency. If the entire TCP session from start to end, then the packet count will be the same, but not in the same order. An example is server is sending several segments and the client is responding with acknowledgements. The packet capture will show all the packets as they are received at the capture point. Send a response, there are different tricks for each situation.

I'm not entirely certain where the 3rd party site you refer to gets its info, likely just a copy of the actual Wireshark documentation, but it's certainly out of date. The perils of not using the actual source of the info.

Either use the help installed with your version of Wireshark which is likely to be mostly in-line with the features in your version, or use the development docs here that may be slightly different from your version.

There is no compare dialog in current versions, it was removed when the UI toolkit changed to Qt, so probably still in 2.6.x if you enable the GTK+ UI on install.

Did you do the merge like instructed?

Compare two capture files. This feature works best when you have merged two capture files chronologically, one from each side of a client/server connection. The merged capture data is checked for missing packets.