Rooting powders are intended for use on woody plants with tough external tissues, so must remain in close proximity to the tissue for a long time and provide high levels of hormones for the duration. Because of those facts, they contain far more hormones than an orchid root system can tolerate, and are not soluble to allow you to dilute them, so I highly recommend you return the product to the store. Instead, look for a liquid rooting hormone product.
The more common ones used on orchids are Dyna-Gro K-L-N and SuperThrive, but there are other brands out there. They contain indole butyric acid and/or naphthalene aceitc acid - synthetic analogs of natural root-stimulating auxins - and when absorbed by the plant, will cause it to start putting out new roots.
The only thing to watch for is the freshness of the bottle - those synthetic hormones degrade rapidly when exposed to heat or light, so become ineffective relatively quickly. (There is a lot of debate about the effectiveness of those types of products, and I'm betting it's due to getting old, "dead" stuff.)
If you get a fresh bottle of either, soak the plant in a solution of 1 teaspoon per gallon of water for about 30 minutes, then repot it. Then, at three-to-four week intervals, add a few drops to your regular irrigation solution.
I have found that there are liquid seaweed extracts, such as KelpMax (disclosure: I have a financial interest in it), that are far superior in effect, and are chemically stable for a lot longer.