There's a part where it asks me on this Form TC-40S (1), "Tax paid to other state must be entered." I have no idea how to find this.

You may find that In TurboTax within the Utah state income tax return.  See the screen Credit for Tax Paid to Another State, 

Yeah, but how do I find the value to put in there?

Review the Missouri income tax return.  Missouri MO-1040 line 36 reports the tax.

In TurboTax Online, you may print or view your full tax returns prior to filing after you have paid for the software.

• View the entries down the left side of the screen at Tax Tools.
• Select Print Center.
• Select Print, save or preview this year's return.

In TurboTax Desktop, select FORMS in the upper right hand corner of the screen.