Schrottbergen is the dative / plural of Schrottberg (m) which is a compositum of Schrott and Berg. Schrott (m) is scrap metal, in our case judging from the context (Gebrauchtwarencenter = Used Car Center) scrap metal from cars. Berg (m) is a mountain but in this context I would rather use something like 'a heap' or maybe 'a pile'. So literally a Schrottberg is a 'mountain of scrap metal', personally I would perhaps use a 'heap of scrap metal'.