You don't need to ask anybody. Graves are numbered to make them easy to find on a graveyard. In the case of your relative, the identification number is: Plot: XIII. A. 7.
The "Find a Grave" memorial website is a marvelous thing. There are thousands of individuals helping to identify graves and photograph the tomb stones.
W.r.t. U.S. (or Canadian) Memorial Graveyards, where the fallen of the different wars are buried, it is the U.S. (Canadian) Government that uploads the basic information to the "Find a Grave" memorial website to help the family of the fallen identify the last resting place of their loved ones.
These (mechanically generated) military memorials are necessarily bare-bones, i.e., they don't offer much information beyond the name/rank of the soldier and his date of death.
If you have more information about a fallen soldier available, such as his date of birth or the name of his spouse or whatever, you can contact the person currently in charge of the grave, and he'll gladly transfer the ownership of the memorial to you so that you can add additional information as you see fit.
If you click on
CWGC/ABMC, the link will tell you how you can contact the current owner of the memorial.