I'm trying to call a ring group thru the flash auto attendant. What would the extension number be to call ring group 5 thru the CCR tree xfer destination?

Ring Groups do not have DN numbers nor can they be called by a phone or CCR.
Expain in further detail what exactly is to happen and what modle phone system and the software.

You probably mean a HUNT GROUP.

You set up phones to be in the hunt group.
When you do the first thing it shows when you choose the hunt group is the DN.,

Thanks for the help