If you want the image printed at 200 PPI then your image needs to be 1600 x 2400 pixels. The math:
8x200=1600 pixels on the short side.
12x200=2400 pixels on the long side.
The PPI setting has no bearing or influence on the quality of the print. It could be set at 72, or 200, or 300, or 600. But the image if printed at 8 x 12" would be printed at 200 PPI.
