Per this it should be there - https://apps.juniper.net/feature-explorer/feature-info.html?fKey=1039&fn=DHCP%20snooping
See here for details on how to configure - https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/port-security-dhcp-snooping-cli.html
QFX51xx and EX4600 have different CLI structure than EX4300/EX3400/EX2300, that is other EX ELS switches.
