Several Avery file folder labels are 30 per sheet, 2/3x3-7/16 inches. The different numbers represent different pack sizes, adhesives or printer compatibility (inkjet or laser or both), but they share the same template. Note that there is a different template for file folder labels with a color stripe.
You can design white file folder labels using the 5366 template in Avery Design & Print Online.
You can also use a template built into Microsoft Word or download an Avery 5366 template for Word, Photoshop, Illustrator, InDesign or Pages.
Here's some information on recommended printer settings.
If you want more information about a specific Avery label, search for the product number on avery.com.