How to pass 128bit Hex number through pointer

Hello,

I have a code for AES-CTR128 made in assembly. The code is linked to a DLL.

Now, I want to use this DLL for computation.

This is what will be on the input for DLL:

• Key: 0x2b7e151628aed2a6abf7158809cf4f3c
• Counter: 0xf0f1f2f3f4f5f6f7f8f9fafbfcfdfeff
• Plaintext: 0x6bc1bee22e409f96e93d7e117393172a

There are several questions I can't solve:

• What data type to use to define all the above?
• What libpointer data type to use to pass args to DLL?

Should I convert it to binary data type? If so, what kind of libpointer should I use?

I'm little bit confused about it.

Thanks for any advice!