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.