We use be + infinitive in a formal style to talk about plans and arrangements.

The meeting is to begin at 6 o’clock.
The Prime Minister is to visit Japan next week.
The train is to arrive at 3:00 pm.
I am to get a wage rise in April.

Be can be followed by a perfect infinitive (to have + past participle). This structure is used to show that a planned event did not happen.

I was to have finished work last week, but I couldn’t.

Be + infinitive is common in if-clauses.

I knew that I would have to work hard if I was to win the first prize.

Orders

The structure be + infinitive is often used to give orders.

You can borrow my car, but you are to bring it back before 10 o’clock.
You are to do your homework before you can go out and play.

Be + passive infinitive

Be + passive infinitive (to be + past participle) is often used in notices and instructions.

This cover is not to be removed.
She was nowhere to be found.