GPSBabel is described as 'converts waypoints, tracks, and routes between popular GPS receivers such as Garmin or Magellan and mapping programs like Google Earth or Basecamp. Literally hundreds of GPS receivers and programs are supported. It also has powerful manipulation tools for such data' and is an app in the Travel & Location category. There are three alternatives to GPSBabel for Linux, Mac, Windows, Android and iPhone. The best alternative is Wikiloc Outdoor Navigation GPS, which is free. Other great apps like GPSBabel are RouteConverter (Free, Open Source) and KMLCSV Converter (Free, Open Source).
KMLCSV Converter is a free open source software that enables you to convert KML file to a formatted CSV file, and vice versa. This CSV file can then be uploaded into your Garmin GPS by using Garmin POI Loader, which can be downloaded for free.