You seem to have tried every combination except the correct one:`
You seem to have tried every combination except the right one:I don't know how to say that some of Iranian people can speak Azeri.
Would you please help me with it? If you were me, how would you say it? (I want to use 30,000,000 in my sentence)
"Thirty million Iranians' mother tongue is Azeri."
(Don't start a sentence with a numeral.
Don't write '30 millions'.
Don't write mother's tongue.)
Consider this instead:
"Azeri is the mother tongue of 30 million Iranians".