I'm a little rusty on cryptography, but I have successfully acquired a 256 bit key that is used for encryption and I want to know if it is possible to reverse it into its corresponding plain text password. If yes, how do I do that?
This isn't a meaningful question.
An AES key is simply a sequence of 256 bits. Some uses of AES (eg. file encryption) compute their key from a password through the use of a key derivation function (KDF), but most (such as SSL and most disk encryption) simply generate a block of random data and use that as the key.
Even if the implementation you're working with is one that runs a password through a KDF, reversing it is not practical: virtually every KDF uses a cryptographic hash function, and reversing it means performing a preimage attack -- something every cryptographic hash function is supposed to be resistant to.