For the Suricata feature, see https://suricata.readthedocs.io/en/latest/configuration/suricata-yaml.html?highlight=pcap#packet-log-pcap-log how to enable the pcap log. This has an impact on performance.
For tcpdump I would recommend the manpage of tcpdump but the basic command would look like:
sudo tcpdump -i $INTERFACE -w file.pcap
Where $INTERFACE is your interface where you want to capture and ideally you add some sort of bpf filter to narrow it down to that specific traffic you test.