Where does chief get GEN 3 armour?

I’ve just been reading up on halo armour lore, and can’t for the life of me figure out where chief got his gen 3 mark vi armour he wears in infinite.

I know he wore gen 1 in four, and upgraded to gen 2 in five.

This is seemingly upgraded to gen 3 mark 6 in halo infinite, but nowhere I read tells me where he actually gets this new suit of armour. Perhaps in the huge time skip between 5 and infinite?