Sounds like you were able to do this part?
Now that you have finished picking up stitches along the shaped edge, does the edge continue with a section where you previously cast off 9 stitches? Continue picking up stitches right where you left off, so that you pick up 7 more stitches from the cast off section.
... And continue picking up 8 more stitches between where you have now got to and the center of the back of the neck.
You should now have 37 stitches.
If this doesn't make sense please post again and include more of the pattern context.