What is the appropriate size of the product image?

Approved and accepted Image size of the product

You can upload images of up to 4472 x 4472 pixels with a file size of up to 10 MB. But the platform typically recommends using 2048 x 2048 pixels for square product photos.
These are high-resolution images that give your store a professional and well-rounded look with great zoom capabilities. Keep in mind that for zoom functionality to work your images have to be more than 800 x 800 pixels.