Hi @cvijeta, welcome to :qiime2:!
The error message you've observed:
Is simply stating that you need to train your classifier for your version of :qiime2:. You can do this by using these linked files which appear further down the thread you've already been working through.
Then you can follow the training steps as outlined here to generate a classifier for the version of QIIME 2 that you are currently using.