Hi @arundhati_brasilense ,
For getting data from SRA into QIIME 2, I recommend using the q2-fondue plugin for a streamlined process:
Detailed tutorials are available in the documentation at https://docs.qiime2.org/. After using q2-fondue to download data, it should already be demultiplexed and you can then follow any of the tutorials starting after the demultiplexing step (e.g., proceed directly to denoising).