Help with childs infinity scarf

I am using a worsted weight yarn. How many stitches do I need for a child’s infinity scarf the pattern calls fo 108 sts. I would like it a little longer than the one in the pattern (22 inches). I am using size 8 needles. The pattern is Red Heart sophisticate cowl. I need it to at least wrap around once without being too tight. Any help will be greatly appreciated.

Welcome to the forum!
You could double the number of cast on sts. It looks like that would be a good length to double over without being too tight.
If you want it longer or shorter than that, figure about 20sts/4inches (or whatever gauge you get with your yarn and needles). The pattern is a multiple of 6sts so however many sts you decide to cast on, make sure it’s divisible by 6.