I need to install water pump and need to know the cost already purchase pump
Same labor as timing belt replacement, which you may want to have done at the same time. Probably 6 to 9 hours.
Depends on what engine and drivetrain you have. If it's a v6 rear-wheel-drive, you're probably looking in the neighborhood of about $650 USD. If it's a v8 all wheel drive, then you're probably looking more around $850 USD. That's for a timing belt and water pump replacement at most shops.