What should I do with money earned before I knew it involved riba?

You are not obligated to try to trace, return, or give away money that was earned through riba (or another haram means) genuinely out of ignorance and before you knew the ruling, especially if it's already been spent — the Quran itself addresses this directly in the same verse that prohibits riba: "…so whoever has received admonition from his Lord and desists, he shall have what is past, and his affair is with Allah" (Quran 2:275), which scholars read as forgiveness for past riba dealings undertaken before the person knew or understood the prohibition.

Going forward from the point you learned the ruling, though, the obligation is clear: stop the practice, and for any specific, identifiable riba-tainted funds still sitting in an account or asset that you can point to (as opposed to money already spent and gone), most scholars recommend disposing of that identifiable amount as described in Q5, out of caution, even though you're not sinful for having earned it in the first place. If you're genuinely unsure whether this applies to your situation — for example, if it's unclear how much of your savings came from an interest-bearing source versus clean income — that's a good, specific question to bring to a local scholar rather than try to resolve alone.

Source: Quran 2:275 (the "what is past" clause specifically forgiving prior riba dealings before knowledge/repentance); see also IslamQA.info answer 2492 on disposing of riba income received before knowing it was haram.