Where do I find form MI-8453 I’m suppose to sign and return it within 3 days?

Form 8453 should be included when you print out your tax return.  

Please see Champ rjs's response to a similar question:

If you selected the option to enter a summary of stock sales, then if you e-file, Form 8453 will be included in your tax return so that you can print it. 

If TurboTax told you to follow mailing instructions, or that you have to mail your brokerage statement with Form 8453, then it knows you need Form 8453 and will produce it if you e-file. 

If you file by mail, you do not use Form 8453. You just attach the brokerage statement to your mailed tax return. In either case, you do not have to prepare Form 8453 manually. TurboTax will create it if you need it.