How much pubic hair should a 10 year old have?

There is no exact answer for this because every child is different. Some children devolop pubic hair as young as 7 or 8 or as old as 17 or 18. At 10 years old, you shouldn't worry if you have no pubic hair or lots of pubic hair. It could be long and thick, short and thin but it doesn't matter because it happens at different times for different people and it can grow fast or slowly. If you are worried then the best person to consult is a parent/guardian or anyone who has been through puberty that you trust e.g. older sibling.