I applied for my greencard through marriage about 6 months ago, but I lost my passport and my I-94 before I started my application process, I filed a I-102 form but uscis sent a letter stating that they cannot verify the date of entry I gave them (because unfortunatley I did not remember the exact date of entry, I remembered the month and year but not the day) so they denied the I-102 without an apeal. How can I prove my entry date? Can this now affect my I-130 or I-485 applications? Any advice please?

File a FOIA with CBP to obtain the record of your processing. Now, USCIS has access to the CBP computer systems, so I am thinking that you EWIed or committed fraud at entry. How and where did you arrive in the U.S.?

I don't know what EWIed means but I didn't commit any frauds whatsoever. I came through customs at an airport...I did overstay my time though (6 months). Do u think the CBP can give me my I-94 number as well?

What about the airline ticket stubs? Travel documents. That will show exactly when you arrived.

ICE also has access to those records. You can go to your local ICE office and have them print it out for you.