TBH it sounds like poor communication from the Dell support, and a lack of acual ‘support’.
It sounds like they wanted you to make a ‘system image’ of the existing computer before reinstalling the operating system.
But that shouldn’t need any new partitions or formatting, so I don’t know quite why he seems to have wanted to create a seperate parition for it.
However if somehow the drive got reformatted then that may explain why none of the files you recovered from it were usable.
If you want to recover what were the ‘live’ (not deleted) files before the reformat (rather that the deleted files) then there is a special way to do that.
If you think that the whole drive was formatted in error then I suggest that you try this special method of using Recuva to recover files from a reformatted drive.
Note that as Windows can already see your drive then step-2 won’t be needed. (ie. DON’T reformat the drive again if Windows can already see it).
No guarantees of course, there never can be when attempting any file recovery, but if/when a drive has been reformatted.
PS. Just looking at that linked post it appears to have lost an image when the forum had a software change, I’ll try to get it back (or put a new one there, I think I can remember what it was).
In the meantime I suggest that you watch the linked video, that shows all the steps needed to recover the non-deleted files from a reformatted drive.