yup, trailhiker. 5 Gmail and 1 Yahoo account, huh? Yikes !! This is going to be a pain in the butt, but it's the only way I know how to do this. using your web browser, Safari, or whatever, log into each one of your Gmail accounts, shift click on each message so that it's highlighted, there should be a checkbox on the left hand side of the column, and then click on delete at the top of the webmail page. Keep on doing this, about 40 messages at a time until they are deleted off of the mail server. then logout of that Gmail account, and login to the next one, and rinse and repeat as necessary. . here's how to do that from the Mail app itself (link)(
https://www.techwalla.com/articles/how-to-delete-email-in-bulk-on-a-mac
under mailbox behaviors, you can choose to leave your message/mail on the server for up to a month and then delete it, or delete it sooner, or even delete it when you close Mac Mail.
here's how to delete a ton of mail/messages in Gmail.....(link)
https://macintoshhowto.com/email/improving-os-x-email-bulk-delete-emails-gmail.html
that's maybe the easiest way to do it.
john b