I'm really not sure of your question, but if it is communicating to a 500, then the Logix5K program probably has a MSG instruction there for data table read/write. That should show source and destination tags.
If you are using an HMI, then you need to check the Logix5K PLC/SLC Mappings (Logic Menu, Map PLC/SLC Messages)
Remember too, that the Logix series CPU no longer uses the dedicated 'File' type of register, but is completely freely definable. You can simulate the 'File' registers of older SLC/PLC series by creating arrays, but even so, the method of specifying addresses is different. In your example, SLC N7:70/7 would (if desired) be represented as N7[70].7 in a Logix program. (assuming N7 was defined as an array of > 71 integers)