Etrex Legend is not in compatible devices list of this and raster maps. See Compatible Devices tab.

A card reader and microSD/SD card are required to download mapping to the following devices: eTrex® Legend Cx/HCx, Vista Cx/HCx, Venture Cx; GPSMAP® 60CSx/60Cx; GPSMAP 76CSx/76Cx; Rino® 520HCx/530HCx; Astro® 220; StreetPilot® 7200/7500 (not all devices are compatible with all downloads).
It's in every map page, but it states:
(not all devices are compatible with all downloads).