If you have some, or know someone who does, you could put a small sample of your powder on a white piece of paper and compare it to known F, FF, FFF
If you cannot tell, you could try a flash test by lighting a small pile on a sfae surface outdoors with a long lighter. If it flashes, it mat well be a balck powder. If it just burns fast - especially with color - it is porbably a more modern powder NOT for ML use. Then you could try a light load without ball or patch and see how it ignites.
If that seems to work, you could try a light load with a cotton ball for compression. If that goes bang you are on your own for further experiments.
If not sure wheter FF or FFF - treat it like FFF.
If really coarse, treat it like cannon powder and use for novelties.
I am adventursome - so would handle with care, but I would definitely play with it.
Others may be more cautious and use it in the garden as was suggested.
Disclaimer - without knowing the whole story on the package or contents you put yourself at risk - and the opinions given by the members or participants in this discussion should by no means be taken as expertise by which you should make a decision that could be harmful to yourself or others.