Coinbase tax form - came after I filed my taxes

Because I transferred Bitcoin from my outside wallet - and sold (had to keep afloat as I had no job for over 9 months), it's saying have 56K capital gains because there is no cost basis. The IRS will tax me on all that, and I definitely did not have 56K capital gains. How can I track all the purchases and transfers? Is there a software I should use?