The hierarchy for a custom taxonomy is listed below:
taxonomy-{taxonomy}-{term}.php: For example, if the taxonomy is named “sometax,” and the taxonomy’s term is “someterm,” WordPress would look for a file named taxonomy-sometax-someterm.php.
taxonomy-{taxonomy}.php: For example, if the taxonomy is named “sometax,” WordPress would look for a file named taxonomy-sometax.php
taxonomy.php
archive.php
index.php
url:
/you_site.com/portfolio_category/term_name
Provided that the settings Admin -> Settings -> Permalinks found:
/%category%/%postname%.html