Need to find a pattern in a running file

Hi and thanks!
Actually I'm new to coding in asm, well start doing it several times but got short on time then.
Now back in cracking again it's time to learn it, I'm pretty sure now how to find the pattern needed but not how I shall do the coding.
Maybe someone can help me with it in FASM.

Any help is appreciated regarding the coding, a template how to read and write a file is a good start, the rest I maybe can figure out myself, please in FASM.

meRlin