That's a really long one. Measure from tip to tip, but it looks like a 36 or 40" length. You can knit a scarf with it, but the extra cord can get in your way. For the needle tip size, you need to get a needle gauge for about $2 from the local craft store that sells yarn, even Walmart has them. It has holes in it you poke a needle into to determine the size.
But for a scarf it won't matter so much, just CO 22 sts and knit the pattern until you run out of yarn or reach a length you want. To cast on in pattern, you work the first 2 sts as usual then pull the first one on the R needle over the 2nd one. Then work the next st, pull the first one over, and so on across the sts. Look at the Casting off page to see a video.
sue- knitting heretic