this is a Vietnamese language . Cac means the.. and pac means have no idea

I think "các pác" is "các bác", some young people use the "p" instead of the "b". For example: các bạn -> các pạn. I think so but I'm not sure. it would be clear if you give a whole sentence

It could be "các bác", mean "you all", but was written in an "internet slang" way, just like "y'all". This is a wrong way to spell this word and you should not use it anywhere else but perhaps chatting on the internet.