Odd Hitman 2 installation window on stratup

I’ve tried opening Hitman 2, and for some reason it wants me to confirm the installation of Hitman 2. I didn’t confirm it in case it did something to my game. Should I confirm it? Here’s a picture of the window: https://drive.google.com/open?id=1p3mtw763A9RK8_Re5wchXDF0jjkG7Jjr

It’s not a confirmation, it’s an installation window.
Maybe you or someone else deleted the game by accident?
Do you remember where it was installed before? Go to that folder and see if game files are still present.
If not, then game most likely is deleted and needs to be installed again.
Just do the install and enjoy the game.

Other reason might be is that Steam client changed its folder location, maybe by itself or with somebody else’s help.
If those game files I wrote above are still present, you just need to go to Steam Settings and to appoint the previous folder path as default.
After that close Steam completely and open it again (or just reboot PC) and the game should work again

I searched where the game is supposed to be located, and the entire game is missing from the folder. I will reinstall the game later today. Thank you very much.

Then it seems to be deleted indeed

Wait a minute… I installed the game in another location, but the steam location was the one that was in the window. Do you know what I can do?
EDIT: I’ve tried opening the launcher from the Hitman 2 location but it still opens the same window

First you should decide where to install the game.

Then in this window you can define the desired folder.

The game will be installed in the folder that marked as Default, so you deside where you want to install the game and add & mark that folder as default with right mouse click