Help with illustrating

[Hitchens77]

Hello. I am looking for software for windows 10. I need it to be able to make posters etc. I need it to have lots of varied items i can drag and drop into the main picture. I also need to connect items with lines etc. Its to help my son with homework.
Im really out of depth with knowing what we would need.
ANY HELP to point us in the right direction would be really appreciated!

 

[hang-the-9]

Any office suite will be able to do this, LibreOffice is free, and should contain clipart and diagramming.