I want to multiply some objects, but I only found the Array, is there any Matrix modifier?
Don’t know what matrix modifier is but if you hit ALT+D it will duplicate your object but make them linked so that any changes made to one will be made to all. Hope that helps 
I am not entirely sure what you mean, but you could use 2 array modifiers to create a grid.
It worked. I used 3 and achieved the result I wanted. But how to I make every copy a single object? In the Outliner I only see one, and I want to change them separately.
Does anyone know?
In the array modifier, hit ‘apply’ button
Tab into edit mode, select all verts with a until they are all orange, hit p and then choose ‘by loose parts’
Thank you very much, Photox!