sc fsc....help!!!

I have purchased a pattern for a dragon tail blanket that I am hoping to make for my son for Christmas…problem is they pattern told me to make a sc fsc but gives me no specific length or stitch count. My son is approximately 4 1/2 feet tall. I would like for him to get a few years of use out of the blanket. What should the length/stitch count of my fsc be???

Signed,
A struggling mom.

Can you please post a pattern link the name of the pattern? I see it’s crochet, but a little more info is helpful.

I figured it out. This step was for later in the pattern but was placed at the top of the pattern for some reason. I have little to no experience reading patterns. I learned to crochet from my grandmother and she never used a pattern so I hadn’t learned to read them until recently. I actually finished the tail last night so I have hope now lol.