First of all, your situation is not serious. Now it's all paid off, so it shouldn't matter. If you want proof of non-malicious arrears, it depends on where the loan is. If it is a student loan, it is a loan run by your education bureau and should be opened in your bank. If it is other types of loans, you have to ask the relevant units.

In fact, the best way is to go to the bank where you want to borrow money to buy a house. Sometimes different banks have different handling methods and procedures. For example, I went to the Agricultural Bank of China to apply for a bank card a few days ago, and today I accompanied my classmates to the Agricultural Bank of China to apply for a card. The same is the Agricultural Bank of China, but the same place is different!