This is the Slic3r forum rather than Cura, but many of us use both slicers. Cura uses INI files for storing & loading profiles (i.e. print parameters such as speed, temperature etc.) Assuming that you are using the GUI and want to load a model into Cura for slicing, this needs to be in STL format. Either drag & drop the STL onto the build plate or use "File" > "Load model file"
If that does not answer your question, please give more details of what version & user interface you are using, and what you are wanting to achieve.
Dave
