There are zillions of them in the area (Miami) maybe due to canals in area. I just had lots tadpoles start leaving a pond near the house

Phantoms gave you all the info you need. I did want to add that they need room as adult he has his in 40 gallon tank which is great but if you prefer you can keep them in long plastic storage bin with chicen wire screen top or plastic egg crate held in place.

They sell them at Walmart . Some keep them outside in them just keep it out of direct sunlight and drill few holes near bottom just incase it rains so bin doesnt fill with water.
They love it warm and at night will croak if you keep them outside they seem to enjoy that