NPC Only moves to where the player is, not to the part I told it to go to?

Do you have any script samples? Do you want it to go to BOTH the player and the part? The script below allows the NPC to go to the part with the use of :MoveTo()

local PFS = game:GetService("PathfindingService")

local NPC = workspace.NPC --replace with your npc
local humanoid = NPC:FindFirstChild("Humanoid")
local destination = workspace.Destination --replace with the part that you want to NPC to go to

local path = PFS:CreatePath()

path:ComputeAsync(NPC.HumanoidRootPart.Position,destination.Position)

local waypoints = path:GetWaypoints()

for i, v in pairs(waypoints) do
    humanoid:MoveTo(v.Position)
    humanoid.MoveToFinished:Wait()
end

If you want them to detect a player as well, replace the NPC with your character. If you want them to detect the nearest player, use Magnitude and a while true do loop to constantly search for the nearest player. Then, compute the path and move their humanoid to the waypoints. Here's the Pathfinding article that you might find useful