My dad always do the transfer thing for my photos and videos and saved it to an apps 'my files'...yesterday when i opened my gallery..all of my photos and videos were not in there..so i checked my files..it is also not in there too...so i dont know where to find my photos and videos back..so please help me and reply my messages ASAP
Try restarting the phone. If they are still on the device, it may just have not shown until reboot.
If, however, he is backing them up to another device (computer, cloud account, etc.) then he may well have 'moved' them rather than 'copying' them. This would make them no longer on the phone. If that is the case, you would need to get him to copy them back over to the phone.
Now if they were deleted and/or you for some reason can't ask for copies back, that is another story.
While there is no guaranty that you can get them back. Deleted does mean deleted. There are a few apps/programs out there that 'may' be able to help you recover the data.
A few of the programs you could try would be... DiskDigger, MobiSaver, Android-Recovery and Tenorshare. They are all data recovery apps/programs. There are many others out there, so check around and see which you would rather try. There is also one called RECUVA, that I have heard is free, which you could try.
One important note though, most of these programs are not free. They may say they are "free" or have "Free Trials" and "Free Downloads". Yet to actually recover your data, and get your files back, you may be have to purchase the program/app. Just so you know.
NOTE: For future reference, I really would suggest backing up your data to a computer or cloud. Often. Better to spend the time doing that, rather than to be out all that stuff if the phone dies, things get deleted/erased or it gets stolen.