This work studies the performance of a non-orthogonal multiple access (NOMA) vehicular mobile edge computing (MEC) network in terms of successful computation probability. In this work, we consider a system in which multiple resource-constrained users on vehicles paired applying NOMA offload their subtasks to roadside base stations by utilizing backscatter communication. Each user deploys a partial offloading scheme by harvesting RF energy from the base station to implement local execution and offloading the remaining subtask to the server at the base station. Next, the approximate closed-form expression of successful computation probability is derived by jointly considering the harvesting energy and latency. In addition, the impact of key parameters on system performance is investigated to reveal the behaviors of our proposed system. Finally, the computer simulation results are provided to confirm our analysis.