Need help with crochet thread sizes

Dear All,

am asking for help, because I live abroad, and need to understand what exactly You mean under cotton thread sizes. I am trying to figure out the thickness of crochet cotton threads. There are sizes 3, 5, 10 to 100, but I can't find the information what the ratio of weight to length for each size of the thread is. Maybe anyone has an idea where I can get this info? Or at least the data how to convert these sizes in "tex" measurement unit?

Thank You very much in advance.