It is not clear what you are asking. If you want COBOL code to implement AES 256 bit encryption and decryption, I suspect you will not get any responses. Your best bet would be to find the AES 256 bit algorithm on the Internet and implement it. Beware, however, that encryption algorithms are notoriously difficult to get right and getting it wrong could expose your data with very little effort. If you want AES 256 for PCI compliance, you'd have to find out what is needed to validate your code meets PCI requirements.
If you want a package to call from COBOL to perform AES 256 bit encryption, there is this tool called "Google" on the Internet that allows you to search for such products. Then your company evaluates them, picks the one that best meets their need, and buys it.
If your site has a crypto coprocessor installed on your machine, you may be able to achieve what you want by using it. However, only someone working at your site -- such as your site support group -- could tell you if crypto hardware is installed, and what you need to do to take advantage of it, and whether or not the crypto hardware supports AES 256 bit encryption.