the 1980s ( Eighties ) without the apostrophe is more commonly used. The use of the apostrophe is declining and not necessary !

You say a, one, two, several, etc. hundred without a final ‘s’ on ‘hundred’. Hundreds (of…) can be used if there is no number or quantity before it. Always use a plural verb with hundred or hundreds, except when an amount of money is mentioned: Four hundred (people) are expected to attend.Two hundred (pounds) was withdrawn from the account. the… hundreds [plural] the years of a particular century the early nineteen hundreds (= written ‘early 1900s’)