How to find Serial Number from Service Tag on monitors

We have roughly 350 monitors left at our site that we are trying to track down during our yearly inventory. For some reason, our team used to track monitors using their serial number (20 digit serial) instead of using the service tag. We have found over 200 monitors connected to machines and have the service tag of those monitors from doing wmi calls and getting the info. However, since our inventory db is using the serial number, we're looking for a way to find the serial number when we have the service tag - if possible at all.