To be confirmed members of your marketplace, visitors have to sign up to create an account, accept terms, fill in potential mandatory fields, and confirm their email address. If they don't, they'll be categorized as unconfirmed or pending.
How to find all unconfirmed or pending users
You can view them all in the "Users / Manage users" page of your Admin panel and use filters to display only such users.
How to resend the confirmation email
If a member hasn't confirmed their email address, maybe it's because they've missed that email notification.
From the "Users / Manage users" page, find the user and click the button on the Actions column. Select "Resend confirmation email" and confirm.