Do I need a copy stand to digitize negatives with a Sony Mirrorless Camera

No. There are other ways. You can use a tablet or phone, light table, lens adapter, etc. Google 'digitize negatives with digital camera` for options. Among top results you can see one that uses a tablet and another with a light table. Nikon makes a lens adapter for negatives too and it may fit some Sony lenses or you can use an adapter to fit a Nikon lens onto the Sony mirrorless.

Copy stands are for duplicating prints and documents, not film. While you can use a copy stand with macro lens and light box, using a slide copier is far easier and cheaper.

Except for the film carrier, capture with a slide copier is the same for slides and negatives. The images also need to be processed differently. For negatives, the orange mask needs to be neutralized and colors inverted.

See Using a 35mm Slide Copier with a Crop Sensor