In Fortnite, you'll want to carry a full stack of ammo 10 meters in order to unlock everything related to Purradise Meowscles, Chapter 4 Season 3's midseason bonus skin. The beloved cat himself will already be unlocked by the time you get this challenge in your quest log, but you'll need to complete it in order to unlock his related player emblem. The wording of the challenge--"full stack"--isn't often used in Fortnite, so it's maybe a bit confusing, but don't worry, as we have your answer here.

How to carry a full stack of ammo for 10 meters in Fortnite

A "full stack" of ammo just means you've hit the carrying capacity for a type of ammo. Any type of ammo--light, medium, heavy, or shotgun shells--will suffice, but they each have different requirements for what counts as a full stack.

Because the requirements are actually slightly lower in Team Rumble mode, it may be in your best interest to play that mode, land in a named location with at least one vending machine--Mega City is your best bet, but all named locations have vending machines--and then buy out and/or pick up all the ammo you can. We've listed full stack totals below for each ammo type currently in the game.