If you mean the feature table and taxonomy file used in the example, you can find them in the QIIME2 tutorial "Moving Pictures".
For your own data set, use the feature table (e.g., table.qza) and taxonomy (e.g., taxonomy.qza) you got from your analysis.
If you want to do it in R, follow the qiime2R tutorial on how to import QIIME2 artifacts into R. Then, you can use the R codes in the previous thread to get the number of taxa at different taxonomic level.