Our good friends at Fotoworks Pro do an excellent job of guiding you through the process of determining the required number pixels for your desired print size. The blog post features our 455 mpix Shores at Big Sur printed on four 30×40 metal prints.
https://fotoworkspro.com/blogs/fotoworkspro-blog/how-big-can-i-print-my-image
The size of the Image (pixels) determine the level of sharpness and clarity for print applications. For more discussion on this, refer to: What Is High Resolution?. In general, 300 pixels/inch (or dpi) produce a high quality print. For larger wall murals where the distance of the viewer is greater, much lower dpi numbers will produce a good result.