You have to explain this a bit more. You can do a (custom) retrieve to get all the data of a certain entity. You do not need model reflection for that. Model reflection is only needed if you need info or want to use the structure of your domain model. See also documentation here: https://docs.mendix.com/appstore/modules/model-reflection
For the retrieve see the documentation here: https://docs.mendix.com/refguide/retrieve . For info about a particular retrieve look at the XPath retrieve part in the documentation.
Also see this learning path about XPath basics: https://academy.mendix.com/link/module/22/lecture/129/4.2-XPath-Basics