I waS changing my transmission fluid and I stripped the inside of the drain,

What should i buy and what is it called??

Are you talking about the threads or the square hole you put the ratchet in? I fit is the thredas then you need a heli coil and a new plug, If it is the hole in the plug then you need a easy out set (bolt extractor) and a new plug.:bigthumb:
Welcome to the boards:iceslolan