download gpx file
open gpx with google earth or one of suggested converters
convert to kml/kmx
save to desktop
then transfer to phone (most likely memory card)
then use import function on google maps (on your phone)
then open said kml file
MyMaps is included in the latest Google Maps Mobile v.3.2.1(#17). Sign in to your google account on your mobile phone. Then in Google Maps Mobile click on Menu-then Layers-BrowseLayers- Your top choice should now be My Maps.
or try https://mymapsmobile.com/
that is suppsoed to retrieve your saved maps
(so if thats the case, then download gxp file then save it into google earth then output as kml and save it to desktop. the open with google maps pc and save it. then load up above website)