We study a scalar dark matter (DM) model with two DM species coupled to the standard model (SM) particles via a sub-GeV dark photon. In this model, we find that DM conversion occurs through the dark photon and it plays a fundamental role in setting the observed relic abundance. Furthermore, the two DM candidates can be produced at fixed-target experiments a la beam-dump. Detailed predictions for signal and backgrounds are obtained with the help of MadDump and NuWro Monte Carlo generators. We explore the potential reach on the sensitivity of DUNE near detector and SHiP experiment, and we find that portions of the parameter space will be within reach of the two experiments.