In the experiment for the osmosis or diffusion, the concentrations of the two regions are different. One has higher concentration of substance compared with the other. Since you have placed the sugar solution in the filter paper, the filter paper now contains high concentration.
To know which has higher concentration between the two solutions is the changes in their volumes. For example, folded filter paper with solution of sucrose (sugar) is immersed in a beaker of pure water. You will notice that the volume of the solution in the filter paper is increased. This happens because the water molecules from the beaker enter the filter paper to reduce the concentration of the sugar solution. a