transferring mp4 from macbook pro to ipad ventura

It's supposed to be easy just drag and drop. I dragged 14 x mp4s. It copied just 5 and they all went into Music! Plus, whilst doing the transfer, the process wiped about half of my videos off the iPad! I didn't back up. I know my fault... But can I find the missing files again and how do I transfer videos, clearly mp4s won't work in an audio programme!