1. **State the problem:** We need to find the total volume of a 3D figure made up of small cubes, each with a volume of 1 mm^3. 2. **Understand the volume formula:** The volume of the whole figure is the sum of the volumes of all individual cubes. 3. **Count the cubes:** From the description, the figure has a tall left column, descending steps to the right, and a single cube on the far right. Counting all cubes gives 25 cubes. 4. **Calculate total volume:** Since each cube has volume 1 mm^3, total volume = number of cubes \times volume per cube = $25 \times 1 = 25$ mm^3. **Final answer:** 25 mm^3