“Please enter special code” aircard 754S please advice how to unlock

“Please enter special code” aircard 754S please advice how to unlock
i have QUALCOMM 4G based on AIRCARD 754S - which was unlocked but i did FACTORY RESET and i can't unlocked since i don't have the code - how can i find the code  - i have SIM MEP LOCKED on the device screen 
appcicated for any assitance 

Thanks