Get your taxes done using TurboTax

The cost basis of the stock is the value at the time of the death of your uncle. Your capital gain is the difference between the cost basis and the proceeds. Your brokerage should have that data as well as any reinvested dividends affecting the cost basis. Capital gains tax depends on your taxable income but is generally 15%. 
You can’t report stock sales with the free program. You will be prompted to upgrade.