You can not get a job with CX cargo, at the moment anyway. The cargo only guys are ones who took an early command, a few direct entry captains from when Oasis went down and some ex ASL guys. All these will be PAX fleet also when they get the same seniority of a new captain upgrading from FO although many will retire before that happens. The only way to join CX at the moment is through the cadet scheme, there are no DEFO opportunities and no more separating of cargo and PAX flying other than that listed above.
It is expected that DEFO may start up again in a few years. If you need more info probably best to post in fragrant harbour forum as most of that is CX stuff.
I assume it is for a job as a pilot.