What is the meaning of "عرفوه"?
What is the meaning of "عرفوه" in the following sentence?

وكم يربح أبوه؟ فإذا عرفوا كل هذا اعتقدوا أنّهم عرفوه

I guess it means "they knew him".
But, it would be "عرفواه".
Is "عرفواه" wrong?

Question

What is the meaning of "عرفوه"?
What is the meaning of "عرفوه" in the following sentence?

وكم يربح أبوه؟ فإذا عرفوا كل هذا اعتقدوا أنّهم عرفوه

I guess it means "they knew him".
But, it would be "عرفواه".
Is "عرفواه" wrong?

Answer

If the word ( They ) means two people , we can say ( عرفاه ) . But if it means several people , it changes to ( عرفوه ) . The verb ( عرفواه ) does not exist in Arabic.

Answer

عرف =knew or he knew or mores (it's depend on how you say it )
يعرف =know
عرفت= i knew or she knew (it's depend on how you say it )
عرفوا = they knew 
عرفنا =we knew

Answer

in this sentence it means ( recognized him )

Answer

"عرفوه" is right and your meaning is also right. 
but to make sense the sentence would be  
"وكم يربح ابوه؟فاذا عرفوا كل هذا ما اعتقدوا انهم عرفوه"