Number of position in the soccer field?

The International Football Association Board (IFAB) writes the Laws of the Game (LOTG) that FIFA adopts for International, World Cup play. The laws are published on 1 July of each year and available at http://fifa.com/. The field is described in Law 1.

As you called it "soccer", we presume you are from the USA, Canada, or Australia. In the United States, the National Federation of High Schools (NFHS) and the National Collegiate Athletic Association (NCAA) have their own rule books for each sport including soccer. Their soccer rule books follow pretty closely with the field dimensions and markings as described in the IFAB LOTG Law 1 but there are differences. Youth soccer, as oversee by American Youth Soccer Organization (AYSO) and US Youth Soccer (USYS) follow the LOTG except they shrink all dimensions for players under 16 years of age.