1st option is very easy, the SW version in write on the CCU label.

(if you post the picture I can tell you right way)

2nd-- Do you have Siemens 840D or 810D controlled machine. If yes, you can borrow the HMI from the machine to connect your CCU3 then from menu " Version" you can  read the version

SINAMIC2020

DEAR MEMBERS:

i have some ccu3 that i want check versions of softwares ,please help me how can i check versions is same or different and what is difference between  ccu3 and ccu3.4?and how can i compare all of them?and how can i make all same software.

 I see your 3 CCU's all have same version, 

You CANNOT upgrade CCU without PCMC card

also forget the anything about upgrade CCU this production is discontinued . If you need specific version , only possible search online from market 

SINAMIC2020

dear nulizhang:

thank you very much for reply,in attachment i show label of ccu3,i want know can i use these instead of each other.how can i upgrade this ccu3's without pcmcia card(using software)

You asked about SW version, and as Pee El Sea answered, the last digit is less important 

Also don't worry about Ver. A or C 

go ahead to use any of them