Separating gelatin from Jell-O powder
Not guaranteed:

If you don't mind just wasting the Jello, or winding up with Jello as a snack*, you can try this to kill some time:

Try to dissolve the whole thing in very cold water. Maybe even ice water. The water must stay cold for this to have a chance.

The sugar should dissolve at least some, and with stirring a little more. The sugar in the packet is superfine compared to table sugar if my memory is correct. 

The gelatin will absorb water but not dissolve. so it should precipitate to the bottom.

Decant the liquid off. take care to keep everything cold. 

Then maybe try it all again to further purify.

This should reduce the percentage of sugar in whatever you have.

The flavoring is probably citric acid and esters, so they are probably very water soluble.

The problems:

You will not know precisely what percentage of whatever is left is gelatin vs. other stuff.

You will not know how much "dry" gelatin is left as it will be hydrated now. So for example, will not know how much of your gelatin = 1 tsp of dry gelatin. 

The chemistry
Taking advantage of relative solubility of the components in cold water. This site says gelatin will absorb but not dissolve in water under 40*C (about 104*F).

*If it fails, just heat the whole thing up in a sauce pan until all dissolved (do not boil), stir well, and then pour into bowls and chill.