It's a short form of "us ko".
he = वह to him = us ko [वह had undergone transformation into "us" because it is affected by "ko."] to him (short form) = use
Of course, in this construction one would not literally translate the language as "to him," rather us ko / use tells us to whom the thing (liking of salad) applies.
It is the equivalent of मुझे for मैं or तुझे for तू, but for यह
Maybe this will help: https://www.rocketlanguages.com/forum/hindi-grammar/mujhe-or-main/