A microscope thread is usually a modified whitworth thread, 55 degree included angle, 36 (.70mm) threads per inch. It uses a rounded crest and root, not sharp V.
You didn't say what type of camera, but you may need a short extension tube to get the focal length right.
I haven't made any camera mounts for a couple of years and haven't links anymore to any websites. But Google 'C-Mount to microscope' or 'Camera microscope adapter', you should get something. There was one site were the user gave very detailed sizes for focal lengths for different cameras and the adapters to microscopes.
The 27th edition of Machinery's Handbook gives the sizes for different microscopes threads, I have to load it here...I'll post them later.