No, sorry, there's no way to bulk upload posts into Voice. You would unfortunately have to re-post them manually.

I guess, you might be able to get an AI assistant to post them on your behalf, by reading your existing blog and telling it how to log into your Voice account to post things. The assistants do have the ability to access the internet and I assume they could also post to a form. But I haven't tried this so would hesitate to recommend it!

You could always experiment on the test site first...

Thanks

Joe