When WW2 started, there were 2 groups of nations fighting against each other - the Allied Powers and the Axis Powers.
I have attached a blank world map that you could colour in two different colours to show which countries were on which side. Use a key to show me which are Allies and which are Axis.
You might need to use an atlas, google maps or the attached world map to find some of the countries.
As an alternative, you could design a poster or information page to tell me all about the nations in each of these groups.