I have been accused of copying two lab reports from the previous year even though I had done everything by myself
In this kind of hearing, evidence will be paramount. "I know I did not cheat" isn't sufficient - that's just a denial. You need more, e.g.:


Can you show that you could not possibly have known about these 2 reports?
Do you have drafts of the report, preferably with time stamps, as you were writing it?
Did you work with anyone else? If so, can they vouch for you?


Offering to redo the reports won't work unfortunately - at this point, it's about academic integrity, not about the grade you get. It's likely advisable to get advice from someone familiar with your department and the academic integrity process, e.g. a faculty member you trust, or student counselors if available. 

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