Firstly, you could load up each string separately using ReadLine() as you load the file so that the whole file isnt put into one single string. Instead its put into separate strings as its loaded
If you already have it as one string (fullfile$) then you can use GetStringToken() or GetStringToken2()
delimiters$ = chr(10) + chr(13) // these delimiters are line feed and carriage return
text$ = GetStringToken(fullfile$,delimiters$,1)
text$ = GetStringToken(fullfile$,delimiters$,2)
text$ = GetStringToken(fullfile$,delimiters$,3)
This works fine on a windows txt file
CountStringTokens(0 would tell you how many lines you could split it up into
EDIT: arghhh...you changed your original post halfway through me answering!!
With your newly edited version of the original post....just a delimiter of chr(10) would work fine.
Ie.... delimiters$ = chr(10)
So if you just want the position of your chr(10) then you can use
integer FindString( Fullfile$, delimiter$, ignoreCase, start )
then when you have found the first position of a chr(10) you put that +1 into the start value for the second search to find the next chr(10)..... and so on