After you saved your migration (previous step from linked tutorial, specifically “Saving Data”) using command yarn rw prisma migrate dev, you might need to make your first baseline as the error describes. Try;
yarn rw prisma migrate resolve --applied <the-last-migration-filename>
for example
yarn rw prisma migrate resolve --applied 20210316161829_my_lastest_migration
Documentation: Prisma Migrate | Database, Schema, SQL Migration Tool
Edit
Did you get the same error after restarting the dev server?