Start with 2014. From your current year, download the prep file and put it in the /14tax folder, just like your prep file is in the /19 folder. Do the subsequent years (15, 16 , 17, 18) if you have not yet done them. You download the earlier years in your "my account"

https://proconnect.intuit.com/community/tax-return/help/how-to-download-and-install-lacerte-prep-fil...

The new TOOL HUB!! https://proconnect.intuit.com/community/install-products/help/how-to-download-and-install-prior-year...