When printing, there are two options.
Either cut off space from left and/or right when the paper is more square than the photo you sent in for prints.
Or fit the full photo and instead add white above/below to fill up to the full height of the paper.
A good print service should be able to support either of these two options.
The other option is that you create (cropping left and/or right side, or expanding with white above/below) a source file that has that 8x10 aspect before sending it for printing.
I think the operative words here are “a good print service”!!!