Well, I am no expert on this, still trying to get my claim done, but this should be something the VA has sent you too in the first place.
When I claimed IHD and a couple of other things they made appointments at several places. One was a cardiologist and he did his evaluation and said that in his opinion it was associated with exposure. Problem came up when I read his full report and we had been talking and having just a regular visit and he put the wrong information about where I was assigned. Claim was denied and I have been trying to prove exposure on Takhli for several years.
I did recently visit my personal cardiologist and had him complete one of the VA medical forms but they still want me to prove I was exposed.
Just my opinion but if I had to get something to them within 30 days and you can't get that information from your doctor write back and send their own information back to them about "presumptive" conditions related to agent orange or herbicide exposure.
Have they acknowledged that you were exposed??