Sounds like you’ve already done this, but I’ll post the link in case anyone else finds this thread.
You need to make a Shopify account and then go here: https://www.shopify.com/legal/tools/report-an-issue/dmca#/form
You’ll be able to report your issue, and then the Shopify legal team will eventually reach back out to you, once they’ve read the request and have made a decision (or if they need more information/clarification on anything).
I don’t know of a way to expedite this process, but if anyone else does, please feel free to chime in.
Note: I don’t work for Shopify, I’m just a guy trying to help out, as no one else has replied to this yet.