It's possible and can be set up to work in very simple, user friendly fashion, but you'll need to take this one step at a time. You can search this forum by entering "barcode" in the search the forum box to see a lot of threads on barcode scanners.
Here's a few tidbits to get started:
1) It's possible to acquire a barcode font for your computer. With the font installed in your computer and in FileMaker, you can simply format your OrderNumber field to print with this barcode.
2) Almost all barcode scanners can function in "keyboard emulation mode" when directly connected to your computer--say through a USB connection. This means that the computer thinks a user is rapidly typing in info every time you scan a barcode. You can thus enter the scanned data simply by putting the cursor in a FileMaker text field and scanning the barcode.
With script triggers, it's possible to set up a layout such that simply scanning a barcode automatically puts the data in a field and then uses that data in a script to do whatever is needed in response to that scan. If you want to set that up, you will need to first access the technical info on your scanner to learn how to set it to append additional text to the beginning and end of the scanned data and then you'll need to write scripts to go with the script triggers--some of the threads you can find on this subject have sample scripts and desicribe these triggers.
3) if you plan to use a scanner attached to an iOS device such as an iPhone or iPad, you will have a more complex set up to do and I recommend checking the posts on this subject in the FM Go forum.
4) If you will be scanning barcodes while not linked to your computer and then will need to download the list of scanned codes into the computer as a batch, you'll need to determine what format that data will have and how it is downloaded. You might be able to download a list of scanned codes into a fileMaker text field or you may get a text file of scanned codes that you can import into FileMaker.