OneDrive Personal Vault is limited to 3 files for anyone with a free OneDrive account with a 100GB quota. It’s very easy to bypass that limitation and store as many files as you like.
There are several ways to store multiple files inside a single files. Use one of those file types to store all your Personal Vault needs in a single file.
ZIP files – the widely supported compression standard.
RAR – RAR is similar to ZIP but with some better options including ‘Solid’
DOCX – Beating Bots, Spies and Cock-ups show how to use Word as a storage container for any type of file or photo.
The three files can be any size up to the 100GB (OneDrive maximum single file size is 100GB except for work/school accounts at 15GB).