Resize and seperate PNG Poster for Large Print

I have a finished design saved as a png, but the file isn’t set to the exact size I need—1189 mm × 841 mm. Please adjust the artboard so that the final output matches those dimensions precisely, keeps proper proportion, and remains sharp when printed at full A0 scale... (Budget: $30 - $250 AUD, Jobs: Adobe Acrobat, Adobe Creative Cloud, Adobe Illustrator, Graphic Design, Illustrator, PDF, Photoshop, Print Design)