Here's a link to assist you if you filed the 2018 state return and just need a copy: https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/00/27010
Or if you did not file the state return and need to do so, here's a link that can assist you with that as well: https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-prepare-a-prior-year-tax-return/00/25984