I am currently knitting a navy blue and white scarf 8ply wool 30 stitches on 6mm knitting needles. Is this the correct knitting size
Welcome to KH!
Ply is a rather unreliable measure of yarn weight since each ply can be thick or thin which will alter yarn thickness. This maybe a DK weight yarn (~22stitches/4inches). What needle size does the ball band recommend?
The needle size also depends on your tension. Are you a tight or a loose knitter? Do you like the look and feel of the resulting knit fabric?
For me, a 6mm (US10) is a bit large for this weight yarn but then I’m a loose knitter. I’d be working with about a 3.75mm (US 5)
What is the name of the yarn? Do you like the way the knit fabric is turning out?
They are 50g each ball
It depends on the thickness of the yarn.
What is the name of the yarn?
Have you knit a swatch to see if you like the resulting knit fabric?