Although you could theoretically convert standard .jpg files to stereoscopic .jps files it would not help you much. JPS pictures have to be created as 3D from the start and cannot be created from plain JPEGs. So yes jpg to jps conversion is "possible", but it won't work.
Some top end graphics editor can take a 2D picture and add a 3D effect to it (which basically moves the background to mimic 3D), but it will never be as perfect as it would be if it was recorded as 3D in first place.Open JPG file Open JPS file
A popular utility for viewing and converting graphic files