Your question in fact concerned how to use the put command to refer to the contents of a field. I tried to answer that question, although there are numerous permutations that I did not go into.
You are now asking something else. In response, I will say that it would likely be necessary to use HyperCard 2.3 or 2.4 and System 7.5 or above to do what you want, assuming that what you want is to copy files from x to y through a script operating at the Finder level. As far as I know, that would involve knitting together HyperTalk and AppleScript, which is perfectly doable but is certainly not a trivial thing to do without a little more information than you are likely to get on this forum.
I do not think that what you describe is possible in Hypercard v. 1 and in Systems under 7.5, but then, I am not what anyone would call a HyperCard expert.
There are reference stacks in the standard installation of Hypercard 2.4 which go into some of this, and you ought to check these out if possible. There may also be freeware stacks "out there" that are even better. But the scripting manual is reasonably detailed, as it was intended for commercial (mostly small-time Shareware) developers who paid for it, and I would think that you are going to need the manual.