Yarn is typically sold by

Yarn is typically sold by weight rather than yardage, even though most crocheters and knitters would agree that yardage is what is important.Worsted weight yarn is a yarn that would knit at 16-18 st/4 inches.  Red Heart Supersaver is a commonly available worsted weight yarn.  What the pattern is saying is that you want 64 ounches off this thickness of yarn .I don't know how old or recent your pattern is but commonly available worsted weight yarn used to be sold in 4 ounce balls so your pattern would be calling for 16 balls.  There's also Pound of Love, which would be 16 ounches so you would need 4 of these balls.Big box craft stores like Michaels, Joann's, and Hobby Lobby typically carry yarns by Caron, Red Heart, Bernat, Paton's, and Lion Brand.  All of these brands have worsted weight yarns put up in various weights probably ranging from 3.5 ounce to the big Pound of Love size.  Find a yarn and color you like that fits your budget.