just name map 1 "GMAPSUPP.IMG", map 2 "GMAPSUP1.IMG", map 3 "GMAPSUP2.IMG"

Call the .UNL files the same e.g "GMAPSUP2.UNL" and have the corresponding map unlock code in there.
Dump all in "E:\Garmin\" and it should work fine

look aslo here
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