In the year of transition between being a nonresident and a resident for tax purposes, you are generally considered a Dual-Status Taxpayer. A Dual-Status Taxpayer files two tax returns for the year—one return for the portion of the year when considered a nonresident, and another return for the portion of the year considered a resident. Your resident tax return (Jan-May 2018) can be prepared with TurboTax.
All non-resident tax return forms like 1040NR, 1040NR-EZ or 8843, are available with instructions on the IRS website. You can also use software like Sprintax to guide you through the non-resident tax return preparation process.