That's ebikekit.com, or E-Bikekit.
Hard to say which model controller you have, but if it has an external switch, its very likely to run only on 36v.
Others run 36 or 48v.
But since it was a special for the army, no telling what controller you got with it. Pic of it would help me see if it looks like the stock kits. BTW, I worked for EBK almost 4 years, and was loosely involved in product road testing since they started. So if its stock, I will see it.
For sure it will run on any 36v battery that can put out 22 amps continuous. In general terms, something 10 ah in size or larger. Your can change the connector if you like, but if its a round black two prong, you can get it at EBK. Same if its a red and black square housing connector. The square is called Anderson powerpole, and can be found many places.