somehow i found the back up but its not where it is supposed to be. thats why itunes cant find it. how do i restore it?

i download the ios 13 beta 6 a week ago or smth an it worked like a charm so i dont chips or anything internally is damaged :) but that not solving my problem. after downloading the update i still have around 5.5 gigs free let me know if i need more space to upgrade