Are our good acts before becoming a Christian used as part of the base for final judgement rewards?

I have never heard this question before, but I think I can confidently say “No.”

64:6 We are all like one who is unclean, all our so-called righteous acts are like a menstrual rag in your sight. We all wither like a leaf; our sins carry us away like the wind” (Isaiah 64:6, NET Bible).

While there are some deeds that men may do before salvation that are good in the sight of man, there are none that commend man to God. All of our works as unbelievers are the basis for our condemnation (Revelation 20:12-13).