Are you talking the several hundred meg .bin and .dat files you might download a game as? If so that is likely some form of iso format, things were not really standardised during the PS1 era and there are loads of formats that various people would use. Not sure what iso format .bin and .dat belong to offhand (the big formats used were standard iso, .bin/.cue, clonecd, discjuggler and nero nrg, there were so many others though), fortunately several (sadly payware) tools exist that can handle the lot these days (magiciso, poweriso, ultraiso...).
If it is files within the iso then .dat is a generic extension and used by hundreds of formats across computing, indeed it is probably second only to .bin in the generic extension stakes. If we had the name of the game or a file sample then something might be able to be done, as it stands both extensions are too common and shared by too many wildly different formats that it is pointless even trying to guess.