Math km and Metres and mass and capacity

tip 1km = 1000 m lets just say i had to measure Something it was 1000 m but 1km = 1000 m so its 1 km any rounds like 7000 = 7km its division and Multipacation math

so i have a test mass and capacity i have a lunch box filled with food i want to measure my lunch box on a pan balance I found some stuff i can use to measure these are the options eggs wood water bottles or a single piece of paper explain why choose your option. everything holds any secrets that nobody knows and the answer is wood because the wood is heavy but i never said how many you could use Exept the paper i said listen carefully read it again the whole page at least 2 times and if you got it wrong fix it a paper would do nothing or maybe a hard paper if That is even a thing the wood is correct.