Large gun stores, on line ammunition sales.
77mm = 0.000077km
77mm equals 3 inches.
77mm is 3.03 inches.
77mm
77mm is greater.
You can find tomahawk ammo by searching through undead bodies when they are dead, and by going to boxes which refill your ammo.
Ammo-18-dl
8 cm
Ask at your local gun shop where you purchase your ammo.
You will have to contact Marlin to find out.
It seems this caliber is slowly fading. I get mine from Able Ammo.
one meter is 1000mm 77mm/1000 = 0.077 m