My finished project was done using H264 at 50 fps.  Client wants to change it to 29.97fps. ProRes 422

I tried selecting my timeline, hit cmdx changed the setting accordingly on the empty project timeline then cmdv to past it back but it didn't work any ideas how to do this.

Create a 29.97fps (or 59.94i) project and open your 50fps sequence bin through file-open bin. When you double-click the sequence, you willl get a pop-up saying MC needs to convert the sequence to the project's format. You will end up with a copy of your sequence, labeled YourSequenceName.(29.97).Copy.01. You can export that.

What Job says is correct. BUT .....

You need to closely inspect the resulting file as all the 50fps shots will now have Motion Adapters on them to allow the 50 fps to 29.97 conversion.  Make sure you are comfortable with the necessary processing results.

Jef

You might find that creating a 50 fps master and then bringing it into a 29.97 (either Interlace or Progressive) project and outputing from there might be easier for you.  Again - closely inspect the result of the Motion Adapter.

Jef

Jef, I fully agree on the need to check the converted sequence.

I would however argue that creating 50fps masters first could result in problems around cuts, depending on the type of motion effect of course.

That is true Job, but when a 23.976 film is transfered to 29.9i interlace the 2:3 pulldown can cause similar issues around cuts. The scene change can occur on field 2.  This is expected and allowed by most if not all the entities I deliver to.  It even occurs with certain standards conversion options.

If I could not afford a high end conversion then doing as you suggest would be a good option.  But it also does really need to be done by someone with experience AND a monitoring system that properly handles interlace.  Both of those seem to be harder to find these days.

Jef