What happened to them and where were they stored?
If you were using Google Photos you most likely have a cloud backup of them. Some other manufacturer apps might offer the same.
If you stored them on a removable sd card (not "/sdcard", which is really internal storage) then take it out of your phone (so you can't overwrite them), put it in a card reader (cheap to buy if you don't have one), plug it into a computer and run any file recovery software you have or download. Recovering from a removable card is not a problem (as long as the original problem wasn't a catastrophic failure of the SD card, in which case it might be more difficult).
If you had them on the phone's internal storage and deleted them, there's almost certainly nothing you can do. Tell us what phone and Android version and we can be more definite, but unless it's an exceptionally old phone you won't be able to recover them.