C# Finding Position of Hex Flag in Binary File

C# Finding Position of Hex Flag in Binary File

I have been tasked with parsing out (via C#) an image from legacy binary
files with a format that's around 20 years old now; the image data is
embedded in the binary file and is prefixed by a hex flag. Below is the
definition of the flags I am looking for (in C):
#define C_THUMBNAIL 0x0008 /* thumbnail bitmap */
#define C_CTHUMBNAIL 0x000d /* compressed thumbnail bitmap */
How do I find one of these flags (are they even flags?) in the file? If I
can figure out where the flag is and how to read the value coming after
the flag (the size of the image in bytes), I can do what I need. This is
what I have so far:
var binReader = new BinaryReader(new FileStream(fileLocation,
FileMode.Open));
//1. find flag
//2. get image size in bytes
//3. take the slice of the byte array containing the image
//4. write that slice of the array to a .png file.
My original idea was to walk through the binary stream until I found the
flag, but I'm really confused at how, if my hex flag is the number 8
(0x0008 == 8, right?), I'm supposed to find it in the file and
differentiate it from all the other 8's in the file.
Sorry if this is a duplicate question, but I don't know enough about this
problem to know what to research to solve it. I've read the MSDN
documentation on binary files and read some similar questions here, but
can't tell if they answer my question.