Did your parents help you financially?

My parents got divorced and want financial information from me

This is a definite "talking to a lawyer" case. There's a bit of leeway here to sort it out between adults, but "speaking to a lawyer" should be the standard judgment here.

The key phrase for me is:

He claims that my mother did not give me the money I owe and that he wants me to give 4 years' worth of financial reports.

I think it is reasonable to assume from this formulation that he expressly intends to use your financial records as weapons in the legal dispute between your father and mother. Since their intended use is a lawsuit against your mother, it seems very reasonable to say that this is the right time to speak to an attorney.

I cannot speak to your specific family as I only know what I have gleaned from 5 paragraphs of the text, but I can say that "family is family". It is generally recommended that money given to a family member be treated as a gift because debt and family are not mixed up. Basically, what your father is asking is to say that your mother should not be treated as your family. She should be treated like a stranger held directly accountable for her debts.

Well, whether they are treated as family become Should or not, it's your business, not mine. But basically your dad is asking you to treat her like a stranger. As such, one must consider whether you should treat your father as a stranger in the name of equality and fairness. When this happens, a stranger asks you to provide financial information. So the answer is "speak to a lawyer".

If you want to treat them like family (and in general, that would be the usual recommendation), get your father involved and try to understand why he feels the need to use financial data as a weapon against your mother. While I can't say what to do once you get his point, I'm pretty confident that the path to healing always begins with understanding.

Maybe your father is just trying to hurt your mother. Maybe your mom is actually doing something nefarious that hurts you financially. We may never know. But no matter what, don't do anything that could harm your mother unless you believe this is the right course of action. If you're okay with the way she handled the finances, then you really haven't done her wrong.