Hi! I'm a new knitter myself but I'll try to help anyway. Go to the company yarn site, for example Bernat. I think they show the yardage in the description of the yarns. If not, go to www.yarndex.com
. They have tons of yarns listed there which will give you the yardage. I think you need to compare yardage if you want to know how much to get. If what you want to use is, say sport yarn than try to find another sport yarn. If you are substituting, you may need more skeins than the pattern says. As far as sock yarn I haven't made any socks but I don't think it's as easy to find as other weights--worsted for example. You might well need a yarn store or try to buy it online. Google sock yarn and see what comes up. Also when yarn descriptions are given at the sites they often say what needle should be used. Size 8 is often given for worsted. But you may need a different size depending on how tight or loosely you knit. Needle size is usually on the wrapper also. I'm sure the experienced knitters here can tell you a good place to buy sock yarn online!