There are four dwarf scrolls in "Stardew Valley". Each scroll is obtained in a unique way. If you want to find the fourth dwarf scroll, you can use a hoe to plow on any floor below the 80th floor of the mine. There is also a chance to obtain it by finding or killing specific monsters in the mines.
Where to find Dwarf Scroll 4 in Stardew Valley
The last reel has a yellow ribbon and can be found via:
Plow any floor below level 80 of the mine (0.2% probability)
Kill any monster in the mine except the following (0.1% chance per kill)
Skeleton
Snake
Wild Giant
Carbon Ghost
Iridium Bat
Iridium Crab
Ghost Skull