I think it’s the same as the Miller 375 and the Miller 675 and the Hobart 375 as well.
Search any one of those on here and they’ll be some info.
@Cnernberg Welcome to The Forum.
Something like this.
Negative on the electrode. Black
Positive on the work clamp Red
And the trigger is in purple.
Use at your own risk.take a really good look inside your unit before you get started.
https://www.rsmanuals.com/31214/miller-spectrum-875-xt60-torch/page-47/