hi.... i just want to ask that is this correct that " i cant contact my father as i dont know where is his meeting going to be held "
Almost, but not quite!
First of all, you must always capitalise I in your sentences.
A better version would be (corrections are in blue):
"I can't contact my father as I don't know where his meeting is going to be held."
I'm not a teacher, so please consider any advice I give in that context.