How to Find All Unread Messages in Gmail

we have two ways:

A. To view all (and only) unread messages in your Gmail account:

• Type  "is:unread" (or "label:unread") (not including the quotation marks) in the Gmail search field.
• Click Search Mail.

B. There is a way faster:

• Choose Settings-> filters.
• Filters-> Create a new Filter
• Write: " is: unread" ( without quotes)-> Next( you can use test search before clicking Next)
• Ok( there is a box appearing, but click OK if you see)
• the key is: you can see many options for filters
• if you want to delete it-> check the Delete it box
• And Remember to check the Also Apply Filter to..( it will be easier to delate a large number of emails at once)
• You should delete the filter once you finish since it will delete your new emails