Hello, Stack -
I found the following information by going to the Stihl home page:
https://www.stihlusa.com/
On that page, I chose the link to FAQs (Frequently Asked Questions) and came to this page:
https://www.stihlusa.com/faq/
I chose the button named "Get Into Now" which brought me to this page:
https://www.stihlusa.com/faq/products/
I chose the link for Blowers. This is the link to that page:
https://www.stihlusa.com/faq/products/blowers-sprayers/
This is the 6th question on that page:
(Quote)
Where do I find my serial number?
(I chose that question and saw this answer.)
On handheld blowers and shredder vacs, it is located on the bar code label on the fan casing. On backpack blowers, it is on the bar code label and stamped in the top of the cylinder or main crank case. All current serial numbers will be nine digits long and begin with the number 2, 3, 5 or 9.
(End quote)
Best wishes.