convert point coordinates UTM to WSG

Dear R-users,

Can anyone tell me how to convert point coordinates from WSG84 (google
maps coordinates) format to UTM HUSO-31 ED-50. And if I have a map
(shp format) with UTM HUSO-31 ED-50 coordinates, how can I convert to
WSG84 (google maps coordinates) coordinates. Should I install some
external software?

Can anyone tell me the instructions?

Thank you,

Marc