iMessages problem

so my phone deleted 3 of my messages from my phone and I wanted to know if I can cover them I tried everything of going back in erasing everything of my phone is starting it all over but nothings working because I backed up my phone wen all the messages were deleted because I thought it was probably going to be a way for me to get them back but I can’t and they were really important and I was running about to get And it was on my iPhone but now I got a new phone but I still want them to be on my 8+ because I still have the phone I want the back and I need help