Transferring data/files between old Macbook and new Macbook

I have a 10 year old Macbook Air that is running on OSX 10.9.5 (and won't update any further) and just bought a new Macbook Pro. I want to transfer all my data/files between the two, but my Macbook Air doesn't have Migration and won't let me install it. Also, it won't back up using TimeMachine on an external hard drive.

Anyone have suggestions?