Emma,
Very sorry for your loss. You’ve certainly come to the right place for help. We can be pretty tenacious when it comes to sticking with one of our members trying to work out troubles with our beloved makes. Muskrat is one of our gurus here and knows of what he speaks. Though, I had guessed the mechanics of this may be completely new to you. We need to be careful not to give you a drink of water with a fire hose. For openers, would you know the last time your dad rode or even started the bike?
The sump plate Muskie mentioned is at the very bottom of the engine where the engine’s case (crankcase) runs between two front-to-back frame pipes. One of the attached pictures shows a version with a drain plug, the other shows an original without the plug. I’ve also attached a picture of mine. The plug on you bike may be oriented differently from the picture. Seeing how you dad cared for this bike, I’m guessing there is a plug, otherwise, he was committed to original purity, which is also great. If the no-plug type, that’s a different kettle of fish (as a Swede, that should be familiar). Taking that apart requires the right tools, replacement gaskets, gasket sealer, and a lot more hand cleaner. Let us know before digging into that.
Finally, let us know if you would like in-person help from a member. I seem to recall at least one Florida member and one or more in Sweden.
Good luck and keep us posted.
Richard L.