You would manually prorate things using the 186 days (or more days if it was available for rent before that, and you were not using it for personal use).
Yes, you will manually prorate your personal usage for the Mortgage Interest, Real Estate Taxes, and Private Mortgage Insurance, then enter that in the Itemized deductions section.
When the program asks you for the number of rental days and number of personal days, in almost all cases you will enter ZERO for personal days. That is because you used it for zero personal days AFTER it was converted to a rental.
