Good day, Tung:
I see your question. Thank you for sharing it.
Section 188.8.131.52 of the Guidelines and Standards for Tactile Graphics says that for grades 4 and up, "Counting items can be represented by using the letters 'on' for one, "tn" for ten, ... A transcriber's note must be added explaining the use of braille symbols as a representation of the print object." So it's tempting to just use a TN for the shapes in your print, but the example you shared (thank you for posting the print page) is more than just a "counting item".
The shapes in your print appear to be an integral part of the exercise (They are even referenced in the instructions). So, I would advise you to include them as tactile graphics. If there are multiple exercises that include models to be shaded, you could reduce the number of tactile graphics required by including a representation of a ten block, a hundred block and a thousand cube in the preliminary pages and then referencing that prelim page at points in the text where such images appear.
Thank you again for your question; please let me know if you have follow-up queries.