Screen shot app no longer there after disk erase and reinstall of Mojave

The Screenshot app is in your Utilities folder which in turn is in your Applications folder.

As I said it is in the Utilities folder, which is in your Applications folder.

Don't forget about the keyboard shortcuts for creating screenshots and also where they get saved and what type they are saved as, which you do by setting some special "defaults" commands in a Terminal window, e.g.

command+shift+3 ==> capture entire screen to a file

command+shift+4 ==> capture specified window or area to a file

command+shift+control+3 ==> capture entire screen to copy/paste buffer

command+shift+control+4 ==> capture specified window or area to a copy/paste buffer

The second and fourth shortcuts (with the control meta-key) bring up a special screen cursor that looks like a small crosshair, and then you can simply move it using the mouse to one corner of the area and then press and hold your mouse select button and drag out the desired area of the screen to the opposite corner and then release the mouse drag, or just type the "space" key on your keyboard to select an entire application window and then click mouse in that highlighted area. You can also just press the "esc" (escape) key to cancel the highlight/capture event. It takes a little practice, but in no time you will be very good at getting the part of the screen captured you wish without having to run a separate program.

The location and type of screen shots are controlled by defaults settings, e.g. in a Terminal window

defaults write com.apple.screencapture location "~/Desktop/Screenshots"
defaults write com.apple.screencapture type png
killall SystemUIServer

Would change the default location where the screen shots are saved to the folder Screenshots which is located in your Desktop folder, and the second command changes the default type of saved image to "png", and that third command (killall...) forces the changes to become active.

You can also check your current screencapture defaults with the Terminal command:

defaults read com.apple.screencapture

Good luck...