I do not believe that there ever was a translation of a buddhist text into greek made at that time that survived until the present time.
As far as my knowledge goes, the only ancient greek source that deals explicitely with india is the travel report of Megasthenes: https://en.wikipedia.org/wiki/Megasthenes
You might had in mind the greco-baktrian kingdom after Alexander I. in what is today Afghanistan and Pakistan. This has been however not comparable to the ancient greek civilization on the european subcontinent. I think we have to understand this kingdom to be a very isolated one which didn't had much in common with the european greeks except for some greek blood in the ruling class. As far as I know they didn't produce any literature in greek, but one important indian source of this time has survived that deals explicitely with the greco-baktrians, the Milinda Panha: https://en.wikipedia.org/wiki/Milinda_Panha
And of course we have a _lot_ of buddhist sanskrit that was propably written already in the time of the greco-baktrians (or maybe even earlier), but that's a different story.