Garmin is pushing a subscription to something called "Maps Plus" for this device. They claim it includes scans of the classic USGS topo maps (and lots of other stuff).
https://support.garmin.com/en-US/?faq=0QeQKEZzTe3SfxvuUDuUZA&partNumber=010-02812-00&tab=topics&topicTag=region_maps
You might want to ask at that other site I linked to above. Unfortunately, things are pretty dead around here anymore (except for the endless spammers I ban every day
)
Not sure if you will get any help from Garmin, in the past they have just blown off any questions about third party maps. But do let us know if you find an answer.
https://support.garmin.com/en-US/?faq=0QeQKEZzTe3SfxvuUDuUZA&partNumber=010-02812-00&tab=topics&topicTag=region_maps
You might want to ask at that other site I linked to above. Unfortunately, things are pretty dead around here anymore (except for the endless spammers I ban every day

Not sure if you will get any help from Garmin, in the past they have just blown off any questions about third party maps. But do let us know if you find an answer.