When i take a photo, it is saved properly in the "exposures" folder, but as a .dat file, not a png. I even tried converting it and it always give me an error, format not supported or something like that. I don't know if it's because I didn't exxposed it yet, but i can't see the files properly. Any help?

.dat files are located in <world>/data/exposures folder, these are internal and only used in-game.

Photographs are exported to /exposures folder when viewed (screen is opened) and only if you are the author.
/exposure export command can be used to export images as pngs.
Exposure Catalog can also be used to export.