Hi Kumar,
If you specify your query, such as "priority=0", to the 'Additional Query' field on Archive and Purge Rule Detail screen, tickets with Priority "None" will be archived/purged. Out of the box, enum of Priority "None" is "0". Just in case, please check enum of Priority "None" on your server. e.g. pdm_extract Priority.
Hope the above helps.
Kind regards,
Kaori