Evernote has been released less than a week. It is not a Microsoft product.
As released, the current version will probably not allow a huge number of files to be imported - and as a Basic user you have limits of maximum 25MB per note, and 60MB per month upload.
I'd suggest you try making new notes in Evernote to see whether it fits your use case, and if so you could become a subscriber and convert your existing notes by exporting them from OneNote in one file format and importing them or copying them into Evernote. You might need to install an older version of Evernote to do so - those instructions are here: Install an older version of Evernote