The best option for pspimage to jpg conversion would be to use one of the graphics editors sold by Corel, the most obvious choice here being the orel PaintShop Pro graphics software that can its own graphics files ('.pspimage) to common JPEG bitmap image format file (.jpg).
Some 3rd party graphics editors like GIMP might as well be of help here, as at least in some version these programs did support .pspimage files and can be also used on macOS / OS X or Linux platforms.