Share 'collection of 1925-1986 with all maps'

So im new at this whole thing and this is my first time at the site.... i went to and estate sale and saw a quite large collection of National Geographics so i bought them for $20. after doing some research, i found that they could be worth quite a bit of money.  i was wondering if yall could tell me about how much my collection is worth? the collection dates from the earliest at 1925 to about 19…