I created a random key and iv how do I store the key without anyone being able to reverse engineer it?

Question

   class AES
    {
    public static byte[] rndKeyIv()
    {
    RNGCryptoServiceProvider rnd = new RNGCryptoServiceProvider();
    var key = new byte[32];
    var iv = new byte[16];
    rnd.GetBytes(key);
    rnd.GetBytes(iv);

    return key;
    return iv;
    }
    public static string Encrypt256(string decrypt)
    {
        

        //der Text aus der Box wird in Bytes umgewandelt
        byte[] encbytes = ASCIIEncoding.ASCII.GetBytes(decrypt);
        //die Blocksize von AES beträgt 128bits und die Keysize beträgt 256bits
        AesCryptoServiceProvider aes = new AesCryptoServiceProvider();
        aes.BlockSize = 128;
        aes.KeySize = 256;
        //der Schlüssel von oben wird wieder mit ASCII Encoding in Bytes umgewandelt, das 
 selbe wird mit dem Initialisierungs Vektor gemacht
        aes.Key = aeskey;
        aes.IV = iv;
        aes.Padding = PaddingMode.PKCS7;
        aes.Mode = CipherMode.CBC;

        ICryptoTransform icrypt = aes.CreateEncryptor(aes.Key, aes.IV);

        byte[] enc = icrypt.TransformFinalBlock(encbytes, 0, encbytes.Length);
        icrypt.Dispose();
        //das resultat der verschlüsselung wird in Base64String umgewandelt
        return Convert.ToBase64String(enc);
       
        }

How exactly can I use the rndKeyIv method to use those keys inside the encrypt and decrypt method? Im kind of confused.

If I would use that method in the encryption and decryption method there would be 2 different keys and ivs