Buy one of these at a local auto store if you need it fast or Amazon..... Look for 6 or better to be legal. Lots of drivers out there are not legal.. but the reasoning behind the law is safety, not money-making... Higher is better.

https://www.amazon.com/GODESON-88702-Smart-Color-Coded/dp/B0793HMWP1/ref=sr\_1\_5?keywords=tire+tread+gauge&qid=1649634833&sr=8-5

You could just get one of these and never ask people again.