You get that from your mutual fund company. If they did not provide a breakdown, you select "More than one state" at the bottom of the state scroll down list.
If your mutual fund company provided you a breakdown, you are
only interested in your home state*. Multiply the % for your state by your total
tax exempt dividends to get a $ amount (you can't enter the % in TurboTax
[TT]). When asked which state, check the box "I earned tax exempt
dividends in more than one state". In the drop down menu, select your
state and enter the $ amount you calculated. In the 2nd box, select "More
than one state" (at the bottom of the scroll down list) and enter the
remaining dollar amount.
*Your state will tax all the dividends except the dividends from municipal bonds from your state.