Identify a hacker of a tapped network of a pcap file?

Identification of a hacker is rarely possible. All you may get is an IP address that is contacted for command & control traffic, but those are usually compromised systems themselves. So don't get your hopes up.

So what you need to do is to identify the malicious traffic. For that you need to know what the "normal" traffic of the network looks like, and find what doesn't fit the pattern. You can do that by looking at the protocols involved (e.g. via the Statistics menu, using the Protocol Distribution stats), or IPs contacted that seem odd. It will take a while if you're not trained in spotting malicious activity, but often filtering for http requests can be a good starting point. This can by done by filtering on "http.request.method" and looking at the host and URL called in the packets you get.

Another point is filtering on "dns" and check if there's any host names that are odd - again, this is something that will take a lot of work checking things out to see if they're legit or not.