Anywhere you can order metal.pre cut?

[typhoon_driver]

Get yourself fusion 360 to start.

As far as file types, dxf is the standard profile type that any cutting company should accept. I would recommend keeping your parts to 1:1 scale to avoid sizing issues.

There are many more companies out there than K-cut. I did a quick google search and found I had a water cutters just down the road from me that are far cheaper so I've been going to them.