These tutorials provide step-by-step guidance on extracting map archives and installing them onto your GPS device: How to Import TOPO to a Garmin GPS YouTube · ExpertVillage Leaf Group
.gmap folders are generally for installation on a computer to be managed via Garmin MapManager. TOPO1a.7z
: Open the resulting .gmap file with Garmin MapManager to register it on your system. TOPO1a.7z