Ditto. Run, do not walk to a store that carries Nitrospiros in a bottle. Read the label and do not accept anything else.
Do as large a water change as possible to get the ammonia and nitrite as close to 0 as possible.
Since you have taken a lot of media and plants from your other tank dump a bit in there, too.
Yes, use the whole bottle.
Nitrospiros is the active ingredient, the species of bacteria you are trying to grow. It is found in these products:
Tetra Safe Start
Dr. Tim's One and Only
Microbe Lift's Nite Out II
Probably a few more, but read the label to be sure. Do not waste money on anything else.