how do i clear emails from iPad in bulk

In the mail app, over on the left, you will see all mailboxes you have linked to your app. On the lower part of that you will see each account, tap on that and it should being up just that inbox or whatever folder you want. Tap on edit then select all and you can delete them as a group instead of one at a time

Another way could be to access your mail via the web interface, for example if you use yahoo. go to yahoo.com (ignore hwen it wants you to install the app) and sign in. You can then also bulk delete.