IMac :: Burning Home Video Clips - Files With Different Format

I am clearing out my old IMac 10.4 & trying to make sure I am not losing precious memories but I cant seem to find certain home movies without hitting a problem. Some files end in .MOD or .MOI & comes up as file could not be opened & says its "not a movie file". I cannot see the same titles elsewhere but maybe in different formats which would play, I did notice the first time I uploaded them from my old JVC hard disc camcorder, that a named clip would appear it 2/3 different formats but since that was my first time dealing with movie files, I didn't understand it. Now I cannot see where the other different formats are. I have searched but they are all that will come up. There is even one or two which are .DV but again says could not be opened but this time also says "the end of the file was reached".