Why is turbo tax asking me for Roth contributions prior to 2018?

I have a 1099-R for a distribution from my Roth IRA. When I enter that info Turbo Tax is asking me for contributions made prior to 2018. This account has been open for 10+ years so that info is not readily available, I am over 59 1/2 so there should be no tax or penalty. Why is it asking for this? What should I enter if I can't find the answer?