The online version stores three years; 2016, 2017 & 2018. If you need to access further back, you will have to go to your MyCRA account here: https://www.canada.ca/en/revenue-agency/services/e-services/cra-login-services.html
Please see link from TurboTax on how to transfer (if needed):
In TurboTax Online, how do I transfer my information (personal details, carry forward amounts, etc.) from my previous year's tax return?
