I'm not gonna give you the correct answer as I can see this is an assignment and I do want you to learn for youself, but I can give you the process.
Just think of it, how many and which characters are truly in this file?
Remember, for each new line, there's a "\n" in the end of that line. Using this, you can read the entire contents of the file (using the Scanner class as NormR1 said).
Then you use that and split the string into an array. Hint; Only on one place in this array there's a "\n\n" sequence.
By splitting at the "\n\n" you'll get an array of 2, with 1 slip in each element.
I copied your assignment above and I can confirm this process works. PM me if you need more help, hope I was clear enough :)
or, read the file line by line, create a simple object OrderSlip which will contain all the info for one orderslip and, if you know up front how many orders you will have, create an array of orderslips in which you store the info, otherwise, add them to a list which takes only OrderSlips as elements.