I don’t know where to go.
I don’t know where to keep my wet umbrella.
I don’t know where to take her for vacation.
I don’t know where to get second-hand laptops.
I don’t know where to buy wine.
I don’t know where to dispose the rubbish.
I don’t know where to post my letter.
I don’t know where to catch No. 45 bus.
I don’t know where to get off.
I don’t know where to invest my money.