Retirement tax questions

Yes the IRA/SEP/SIMPLE box is marked. So this should be a distribution from a Traditional IRA?
You stated "unless you have made nondeductible contributions to your traditional IRAs, reported on a Form 8606"
How do I determine that?
Nondeductible contributions would be if after tax contributions?
If so, where do I get that information?
That would be nondeductible contributions do I have a basis to consider or ???