The original pattern is K2, K1 in the back, P1 on straight needles for a scarf. I am trying to make a matching hat. How do I get the same pattern on the circular needles? Any guess. I am not sure what to do except maybe just knit on straight and whip stitch together. Help is appreciated.
Are both sides this pattern? If not, what are the directions for the next row?
yes this is the pattern for both sides cast on 26 stitches the last 2 stitches you knit.
For knitting in the round, you’d have to reverse the stitches and the order in which you knit them.
So one round would be k2, k1B, p1, k2
Round two would be p2, k1, p1B, p2
For the sake of your sanity, use a marker for the beginning of your rounds. 
(Guess who figured that out years ago after a couple of not so successful projects…)
I usually figure about 72 stitches for a hat in worsted weight, but that will vary with how tightly you knit (I knit loose) and your yarn and needles. If the scarf has two border stitches on each side, remember to leave one set off unless you want a wide border between pattern repeats. You can knit a couple inches of ribbing, then start into the pattern if you like, and when you want to start decreasing it always helps if you start with the plain stitches.
It’ll work. I’ve done hat-to-match-scarf several times.
Thank you!!!