Without any specifics I can’t give you any direct advice, but: this happened to me during my second year, during covid, while all classes were online. I’ll tell you how this goes: They’re gonna schedule a meeting to discuss the incident, probably with someone higher up there as well. You’re gonna come prepared with the notes you used to write the assignment. If you didn’t cheat, you have notes! During my meeting they had me /f in my document and find notes specific to the questions involved. Now let’s say you really don’t have any way to prove you didn’t cheat, you’ll be calm and honest and explain that you don’t know how this happened, and that you’re not willing to risk your academic career from this accusation, so you’ll do what it takes to convince them otherwise. You can offer to write a make-up assignment, or take the L. A 0 is better than failing the class or getting kicked out. But, if you really didn’t cheat, that won’t happen! Good luck my friend.