Turbotax wants us to enter our individual AGIs from last year but since we filed jointly there is only one number on line 37. How can we determine our individual AGIs?

When you file jointly, your AGI is the same for each spouse - you don't split it or enter 0 for one spouse.  Example:  if your AGI shows $50,000 on line 37.  Then, you would enter $50,000 for you and $50,000 for your spouse for your individual AGI's.