I'm quite sure you can't manually "transform" one 10G SFP+ Copper DAC terminated cable's end into a RJ45 cable's end.
You must provide SFP+ enabled devices to both ends of the 10G SFP+ Copper DAC terminated cable you have or, in the worst case (in terms of both complexity and DAC device-to-device performance degradation you're going to add), look for something like a 10G SFP+ copper <--> 10G RJ45 external Media Converter (like this one).
