DB path issue

[Ione-starI]

I just followed the "Installing the plugin" step by step.

$pip install q2-brocc
$qiime brocc --help
$wget "ftp://ftp.ncbi.nlm.nih.gov/blast/db/nt.??.tar.gz"

I could get 54 nt.xx.tar.gz files in my DB directory (/My/path/NCBI_DB/)
and I copy the path to ~/.bashrc

$source ~/.bashrc

#download test file
$wget https://raw.githubusercontent.com/kylebittinger/q2-brocc/master/q2_brocc/tests/data/query.fasta

$blastn -query query.fasta -db nt -outfmt 7

HOWEVER, I get the message
"BLAST Database error: No alias or index file found for nucleotide database [nt] in search path [/My/Working/Directory/Brocc:/My/path/NCBI_DB:]"

Should I download any other files? or decompress the nt.??.tar.gz files?