Marmalade Orange Jam

My dad's Bitter/Sour Orange tree has produced so much this year, so with so many fruits my mom shared with me her grandma's Marmalade's Jam recipe that she got from my eldest aunt from Iran. 

Ingredients needed: 
10 fruits 
3 kilo suger 

Recipe: 
First soak the oranges for 5 to 6 days in cold water and every day change the water twice. After the 6th day, dry the fruits and shred the first layer of their skin with the grate very lightly. Then thinly slice each orange. Then boil water in a pot and then add the sliced oranges and wait for 1 minute, repeat twice. Drained the oranges, add them to the sugar water mixture that is thickened - cook for 15 minutes. Marmalade is done, keep in the air-tight jar