You need to calibrate by printing an object with known dimensions in each axis. Then measure the actual values on the printed object (you'll need a set of calipers with better than 0.1 mm accuracy). From that you can determine scaling values. Most slicers will have at least an overall scaling value in the filament settings. Orca and its kin have separate scaling for XY and Z. You can also scale the object itself manually in the slicer, but using the filament settings is better because it will be applied automatically for everything you print using that filament profile.