As we know from Hadith. Allah will ask to those person who used to painting animated things, Allah will ask them to give life to those paintings.
Allah's Messenger (ﷺ) said, "Those who make these pictures will be
punished on the Day of Resurrection, and it will be said to them.
'Make alive what you have created.'"
Reference : Sahih al-Bukhari 5951,
In-book reference : Book 77, Hadith 167
It is best if you burn them. Since you didn't know it was haram you will not get any sin.
Repent to Allah
Burn or destroy those paintings
Never do it again
If you don't have any access to some drawing you have drawn in past, and can't able to burn them. Allah will not punish you for that.
Because in surah bakarah Allah says :
"Allah does not charge a soul except [with that within] its capacity."