@Jeremy1214 and if you do mean Biogen, you might just want to assume $0 - it may save you a lot of time
a quick Yahoo Finance search shows the price 31 years ago at $2.84 per share and it is possible you purchased it for even less than that. Even if you purchased at $3 and assumed zero, that is a cost basis of $1380 and even at 23.8% capital gains, it's only worth around $325 in tax difference.
