XML missile poperties?...

So I'm making a Aim-9 sparrow (AIM-9B sparrow to be presice...) and there is that "MaxRange" thing and I don't know what's the equivalent of 1 unit of XML on distance(I use Kilometers) so it's something like this :

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XML EDITOR THING HERE

   MaxRange   /     4000

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And the this is that I don't know what that (we are going to call that “4000„ a "unit") and I need to know what that unit is translated to kilometers because the range thing needs to be accurate

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EXAMPLE :

  4000    =    5km

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I need something like that , to know what is a unit translated to kilometers