Do you have a copy or the original service record of your grandfathers? That would show what unit he served with and where he saw combat/and/or service. If you don’t do you have any info on what unit he served with? That would go a long way to helping get the info you want.
No, but I have found a number that is identified as his serial number. Serial to what, I don’t know. It’s 38137940, but I have no idea how military ID numbers work.
I heard recently that DD214’s are now available online?