How do I make a npc move when I say "Hi" in chat?

Scripting Helpers is not a request site! (But I’ll give you the part that detects if you say “hi” in chat)

local PlayersService = game:GetService("Players")
local StringToDetect = "hi"

PlayersService.PlayerAdded:Connect(function(Player)
    Player.Chatted:Connect(function(Message)
        if string.find(string.lower(Message), string.lower(StringToDetect)) then
            if Player.Character then
                -- code
            end
        end
    end)
end)

local str = "Hi"
local npc_character = PATH.TO.YOUR.NPC

game:GetService("Players").PlayerAdded:Connect(function(player)
    player.CharacterAppearanceLoaded:Wait()
    local char = player.Character
    player.Chatted:Connect(function(msg)

        if string.find(
                string.lower(msg),
                string.lower(str)
            ) then

            local npc_hum =
                npc_character:FindFirstChildOfClass("Humanoid")

            if not npc_hum then
                return
            end

            npc_hum:MoveTo(char:GetPrimaryPartCFrame().Position)
        end

    end)
end)

haven't tested

Scripting Helpers is not a request site it is a website where you ask the community to help debug errors with your code and help other people debug errors with their code.