How to move mail.app emails to Gmail?

Hello,

I had mistakenly moved my gmail to mail.app - mistake was that I completely cleaned-out my entire Gmail account! I fixed Gmail so that it copies the emails as they go to mail.app, leaving it also in Gmail.

Now I want to restore the 3,000 emails I had cleared out of Gmail BACK into Gmail...can I do this?

Can I move them somehow from mail.app back into Gmail with one sweep, just as I had moved them all into mail.app from Gmail? Or am I skrw'd and have to move them individually by forwarding?

Anybody have the same issue or answer? Thanks much, -Joe