When you connect your Kindle with the USB cable to your computer, you have the option to view the files on the device. The Documents folder is where any and all of your ebook files (compatible with the Kindle of course) should go.
If you want to browse those files, or are looking for a particular file, sifting through all those file names can be a pain. It can help sometimes if you can sort the files so the one you want will be easier to spot.
In this image, you can see I circled the top row where the names of the columns are. This is on a Mac, but is very similar on a PC, and clicking each top column once will accomplish the same thing on both.
Click the name column once and your files will be sorted by name. Click the date column and the same files will be sorted by date. This should make it much easier to find what you are looking for.
If you don't see the columns:
Look in the menu bar just above the column names... you will see 4 buttons on the left side. The second button from the left is the details view button. If you just see icons or pictures instead of your files and columns, click this button so you can see the files lined up and down in the window. On a PC, click the word view at the top of the window, then click the word details to see your files listed in this view.