adobe photoshop - What file sizes and formats are most appropriate for enlarging and projecting an image onto a large wallspace for painting?

I think my title question says it all. I have hand drawn some designs (A3) that will be projected onto a 9m X 7m brick wall. This design will be painted as a mural.

I'm concerned about the appropriate file size and format to use as I need to retain a clear image to work with.