It depends on what type of LLC it was. If it was a single member LLC and the business activity has been reported on Schedule C, go to the Schedule C section of your return (Search for schedule c and select the Jump to link in the search results) and select to "work on" that business and you should be asked if the business was sold or disposed of during 2018. See the sample screenshot below from Schedule C business info in TurboTax Home & Business.
If your LLC was a multi-member LLC, then a final 1065 form would need to be filed. Again, in preparing the return, in the Business Info section, you can select that the business ended/disposed of in 2018.
Enter your E-mail address. We'll send you an e-mail with instructions to reset your password.