Sometimes, data belonging to Relational databases need to be transferred to NoSQL ones. However, the data conversion process between Relational to NoSQL databases is considered as not trivial, since it is necessary to have considerable knowledge about the data models at hand. Regarding the structural heterogeneity underlying this problem, we propose an approach, named as R2NoSQL, which defines conceptual mappings to enhance the data conversion process. In this paper, we present our approach and some implementation and experimental results, which show that, by using the defined conceptual mappings, we obtain a consistent target NoSQL database with respect to a source Relational one.