Here are the reported speech conversions for the sentences you've provided:

6. "Will it rain tomorrow morning?" he asked his friend.
He asked his friend if it would rain tomorrow morning.

7. "Where does your father work?" the teacher asked me.
The teacher asked me where my father worked.

8. "How many people are there in your family?" he asked Lan.
He asked Lan how many people there were in her family.

9. Tam asked him, "How long will you stay in England?"
Tam asked him how long he would stay in England.

10. Peter said, "I want to tell you the news. You must be surprised."
Peter said that he wanted to tell me the news and that I must be surprised.

If you need further assistance or have additional sentences to convert, feel free to ask!