No launchpad. how can I add launchpad?

Try Command L (⌘ L)

If that doesn't work go to Apple > System Preferences > Keyboard > Shortcuts > Launchpad & Dock and check the Show Launchpad key command.

Another way, is to setup a Hot Corner.

go to Apple > System Preferences > Mission Control > select Hot Corners... and setup a Hot Corner to Launchpad.

Also, you will find the Launchpad app in the Applications folder.

Find the app there, drag it to the Dock and release. The icon will remain in the Dock for your convenience and the app will continue to reside in the Applications folder as it should.

Please see > Use the Dock on Mac - Apple Support