Screwthreads help?

hey all

for my design class i am in need of creating a screw thread and am lost, any help is appreciated

If they are standard threads, you can download models of screws, bolts and nuts from

I would add download using safari , I have had Chrome mess up models downloaded.

Question: Do you need to create a screw thread yourself for your project?
Or, can you use an existing one and download it as suggested?