If you haven't started your 2019 tax return yet or are willing to start over, see these instructions on how to upload your 2018 tax file for transfer into the online version of 2019 TurboTax:
https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-...
Otherwise, your IRA contribution basis is captured on the IRA Information Worksheet in your 2018 tax file.
