Marines don't use bumper numbers for ID, but it looks like maybe the unit ID is right there in the photo with the emblem, just need the last number of the UIC.
All Marine units have a UIC (Unit Identification Code), it is an M followed by 5 numbers. It is usually somewhere on the door of MVs, sometimes also on the back and occasionally on the front. On Humvees and vehicles without hard doors, it is usually on the body under the door opening.
Below is a good example on my M813. M21640 is 8th Comm Battalion
If you can get the complete number, I can look it up on my list.
Cheers