You probably need to add (or, subtract?) a washer-or-two between the caliper & the mounting tabs to center the pads ...
So, loosen the caliper ... center the pads & see how much gap there is between the caliper & the disc brake mounting tabs -- I think that generic, #10 washers from the hardware store will work ...
You can cut 0.2mm shims/washers from an aluminum soda/beer can.
Try SANDWICHing the rotor between TWO pieces of file folder cardboard (or, equivalent) OR whatever thickness of cardboard works for you (e.g., cereal box?) and slide the caliper over the combination while you are trying to ascertain the offset the caliper should be mounted at ...
Presuming you have a traditional 6-bolt rotor, I suppose it's possible that putting washers/shims between the rotor & hub might be an alternative.