text program

[Reigan]

I need code, who take some string of character, and to compare that a .txt file.
example:

string = "qwe"
.txt file = ''axcbhyQWEklmnpouyxsQWElkopyqQWEsd''
(7) (20) (29)

I need then program find in this text file a letters: ''qwe'' and call the number of that place, where this leter start in text.

result must be:
7, 20, 29

please help me.