Importing cover art without needing to resize image to fill page

Hello, I am trying to upload a cover art image in MuseScore so that the artwork covers the entire page after I upload it into MuseScore. The score I have is 9x12. I have the artwork generated at 2700x3600, which in theory should cover the whole first page when I use it in MuseScore. Hopefully one day I can have this printed and bound, like a Dover or OmniMusic Publishing respected published scores. My question is, with the end goal of printing and binding in a soft cover booklet in the size of 9x12, how do I adjust my artwork so that resizing the image and going off my eye as I drag it to fit the page, is no longer necessary. Thanks a lot.