i need a tutorial because i simply can't make this work, i'm trying to add a generic.attackDamage to zombie to make him do more damage but it doesn't work and the zombies keep doing 1 damage even without me wearing armor, i just need a video teaching me how to do this little thing because i don't know how to code

here's the codes that i tried

zombie;generic.attackDamage;1;1.0
zombie;generic.attackDamage;1;2
zombie;generic.attackDamage;1;2;/;1
zombie;generic.attackDamage;0;5

an image if it helps to see what i did wrong