Baby Cashmerino is a much finer, slimmer yarn than the worsted weight called for in the pattern. If you cast on 107 stitches & work with the US3.25 needles, your blanket will only be half as wide. It will still be lovely, just smaller.
You can work the pattern with a double strand of yarn. Two strands carried together & worked as one on the larger needles. Which will double up the thickness of the yarn. But requires twice as much yardage as well.
Or you can start with more stitches cast on initially & add more rows of stripes. And use the smaller needles. That will make the blanket larger.
Either way will be pretty.