It's not clear from your question whether you are just trying to recreate the image in your question, draw a 3D grid, or draw something with a 3D grid for reference. Wrzlprmft's answer already covers drawing something like your image, so I'll cover the other two.
Draw on a 3D grid
Inkscape has a grid that you can used to guide your drawing, such as snapping points to it. To show the grid, on the View menu click Page Grid or press Shift + 3.
The default grid is 2D. To use a 3D grid, do the following.
- On the File menu, click Document Properties.
- In the Document Properties on the Grids tab, in the Creation box, select Axonometric grid, and then click New.
If there is an existing grid in the Defined Grids, you may want to deselect Enabled or just remove that grid.
- If not already visible, on the View menu, click Page Grid.
You can use the snapping tools so that when you draw or move, it'll snap to this grid. If you don't see the snapping tools, on the View menu, hover over Show/Hide and click Snap Controls Bar.
Draw a 3D grid
If your goal is to draw an object that looks like a 3D grid, use the render isometric grid extension. This is found in Extensions > Render > Grids > Isometric Grid. Experiment with the various options to get the grid you want (or close enough), and then manually edit it by hand if needed. The rendered grid will be a drawn object that you can manipulate and edit.
This would be an alternative to draw something similar to your posted image. Render a grid with a size of 1 in all directions and change subdivisions to 0. Ungroup it and delete paths you don't need, and then make the remaining stuff look however you want.