For an autobiography, which element of your final draft will you consider to evaluate the richness of your details?
use of language
elaboration
audience and purpose
organization

So, you're evaluating the richness of your details, that is, you want to know how rich your details are.

From the options provided, the best one is "elaboration": it can be understood as "adding details"  

But actually when you evaluate a text you wrote all of these options would be good to consider: so how good your organization is, etc.