In the byte array i want the equivalent hex values (FF)
If the target is an array of bytes and the source is "FF" then I assume that you want {255} in the target.
Bear in mind that HEX is only a way of representing the value of a byte in a way that is easier for humans to read than binary. An 8 bit byte may be said to hold 0b11111111, 0xFF or 255 and it will still have the same value.