The tax value of real estate can only be found on the property tax bill that is sent to the owner of the property. If you are a renter and do not own the property, I see no reason for the program to be asking you for the tax value on the federal return.
However, some states give a "renter's credit" on the state return and "may" use the tax value to determine how much of a credit you get based on the tax value of the property and the amount of rent you paid to the owner of the property during the tax year.
If you are not the owner then obviously you will not be the one with the property tax bill. However, what you seek is public knowledge. I would expect you to be able to find it on the website of the property tax appraiser for whatever county/city/township or other jurisdiction you are in.
Might be able to start at https://www.michigan.gov/taxes/0,4676,7-238-43535_43925---,00.html
