UMS hasn't been available for years now. I'm afraid the solution is to have your backup made before you erase the data (it's a good idea to have backups anyway, because if you lose the device recovery software is irrelevant).
I'm not aware of any way. You'll probably get posts telling you to use some shonky "android file recovery" software, but I've never seen a real world report (as opposed to one written by the vendor) of those things working.