Lost Onedive and Onenote Documents

I have been using one computer for the last 7 years. The other day I opened it as normal, but to a screen of "bitlocker key". I have no idea what this key is, and after taking it to multiple IT people, and them saying there is nothing you can do without the key, I ended up buying a new laptop. I knew that I would loose everything on my desktop, but 90% of my work is saved to onedrive, or in onenote folders, so I assumed that I would be able to log into my new laptop on the same account and for everything to be there. When I set this laptop up yesterday and went to sign into my Microsoft accounts half of my files are missing. Nothing is in folders like it was before, there are documents everywhere, as well as some not being there at all, or being able to see the document, but it saying that I am not the author or the document does not belong to me. Some of the other files are also saying "the file format or file extension is not vaild. verify that the file has not been corrupted and that the file extension matches the format of the file". There is not a certain date that the work has stopped being saved, it is all random. The same thing is happening on my onenote, I cant see one whole notebook, but others are there that were created at the same time, and saved under the same account. I would really love some help with what to do!