Emergency action codes

I am an adr tanker driver who normally just pulls one product so know what markings I should be using. However im going to start pulling multiple products and there is some confusion on the emergency action codes that should be marked on the barrel.

I have two products a class 8 with un 1760 and a class 9 with un 3082. At the moment I’m being told that I should have 3X on the rear with no un number can anyone tell me if this is correct or where I can find out evidence to prove otherwise.

Thank you for any advice all is welcome and appreciated.